Replacing fork springs R100S - easy or challenging?

[JohnnyMoto68]

Howdy - my 1977 R100S (love) sounds like a steam engine when I push down on the front end. If I hold the front brake lever and push forward, I can hear air hissing from the front forks and the forks compress fairly easily - the bike has very little proper damping action up there.

I did a fork oil change last night in the hopes that it might rectify, but no luck. I put a bit of extra oil in as a countermeasure (which did help), but methinks I need new springs. I don't want to blow the seals out - extra oil is just a temp solution, and I'm garaging the bike until I figure this out.

I think I'm ready to switch the springs out. I haven't done this before, but I've seen it done on other bikes and I'm pretty sure I could figure it out if it's not a huge job on this bike.

So, a few questions, O Airheaded Ones:

1. Do I need to remove the forks to do this operation, or can I pull the fork caps, and thus the springs directly from the top of the forks and drop in the new ones? (In other words, can it be that easy?)

2. Are there serious risks of front alignment going out of whack, etc? If it's a pull out/drop in kinda deal, I can do that. Otherwise, if this is surgery, I'd rather take it to my local mechanic. I've got a Clymer, but they don't always make it crystal clear. (Type I fork? Type II fork? Er, my bike isn't listed guys...)

Bonus question - where's the noise coming from? Is it possible that I have some valve that's stuck in the open position? Any help/advice greatly appreciated - a good link describing this procedure, that would be fantastic!

Thanks mucho -

[AnnapolisAirhead]

If there is a hissing sound, you might have bad seals so even new springs wouldn't help. The forks are hydraulic, so the seals need to be there to function properly. Putting new springs in with leaking seals is just tossing money away.

I just did my first fork oil change with the help of several folks. I can't recall what the forks on your bike look like, but my guess is that you need the same 36mm (yes, 36mm) socket to remove the big nuts under the triple tree. The fork lowers (on my bike anyway) drop out too, but there are more steps than that. You've obviously figured out how to drain them, but they probably should be cleaned inside, new seals and the exact amount of and proper weight of fork oil fluid. Adding some extra in for good measure is likely to make a leaking seal problem even worse and could be downright dangerous.

I found Clymers to be an invaluable resource! Do you have any pics? I found a 1977 R100S in Clymer's (release M502-3), but nothing specifically for fork oil changes. I am pretty sure your forks are the same as the RS. I could be wrong, but a call to your local BMW shop could confirm--you'd have to do that anyway to make sure new springs would fit if that's the route you go.

Hope that helps. :drink

[lostboy]

If your bike has gaiters on the forks, the hissing sound is probably coming from the vents. They are vented via split pins which pass through the the lower triple clamp.

Fork spring replacement on your bike is relatively painless-support the front of the bike, remove the handlebars and top plugs and old springs. Drop in the new springs, set the preload, torque the plugs and reinstall the handle bars. I reccomend either Progressive Suspension fork springs or BMW "017" springs.

[88bmwJeff]

Given what you said, I would rebuild the forks; however, it's hard to tell without seeing it in person. Rebuilding the forks would include new seals, and springs as needed. If you have a good relationship with a local mechanic, you could swing by and their opinion.

I know some people leave the tubes in place, while others remove them. I believe you would have to put a few blocks of wood under the center stand or have the bike on a lift in order to leave the tubes in the triple tree. However, if you are having the forks rebuilt, it's a perfect time to serve the steering head bearings. If these tasks are above your ability, then perhaps you should take it to your mechanic; however, if you're willing to go slow and work through each issue as they arise, you could do the work yourself. If you do the work yourself you do need to make sure the forks are properly aligned. Otherwise, you could end up with stiction.

[R80andR100RT]

I always use a little permatex on the threads of the cap nuts so they seal up tight. If you are going to remove the forks as Jeff asks its a perfect time to install gaiters. It will be the last time the bike needs fork seals replaced. They will fit on an RT just pull off the boots where the fork goes thru the fairing.

[AnnapolisAirhead]

I always use a little permatex on the threads of the cap nuts so they seal up tight. If you are going to remove the forks as Jeff asks its a perfect time to install gaiters. It will be the last time the bike needs fork seals replaced. They will fit on an RT just pull off the boots where the fork goes thru the fairing.

I've been wondering about whether or not they fit. Are all airhead gaiters the same size? So I could order for a 76 R90/6 and could fit them on my '83 R100T? That'd be a dream, keep em clean for life. :clap

[JohnnyMoto68]

Thanks, all! Going w/ Progressive springs, ordered from Bob's. I also ordered various and assorted washers which I will replace during the work.

I appreciate the comment on the steering bearing work, but I will wait to get to this at another time...I have all winter to break stuff, right now I want to get riding. :eat

Question - one reader mentioned setting the preload. How do I set the preload on front suspension? Don't I just drop the springs in and away we go? Or do I need to worry about spacers and all that jazz...

Thanks -

[Isamemon]

when I got my progressive springs they came with a pvc spacer. I have read that people play with the sixe of the pvc spacer to get differnt preload
maybe the archives will help there is also a real good website on rebuilding the forks, but again you will have to google it on your own

[rpeckham136133]

Question - one reader mentioned setting the preload. How do I set the preload on front suspension? Don't I just drop the springs in and away we go? Or do I need to worry about spacers and all that jazz...

Thanks -

I have Progressives on my /6, and as long as the springs are longer than the tube (i.e. they stick out the top until you screw in the top piece whilst you push them down), they are going to be preloaded to somebody's specs.... If you want them harder, you could put in a spacer to make the spring more compressed while at rest. You can play with that if you want a stiffer ride, etc.

[JohnnyMoto68]

Howdy - I finally got around to pulling the handlebars and then pulling the top fork caps off the bike. I also got a 36mm socket for the top nuts...and discovered to my dismay that they are absolutely, absolutely frozen solid. I'd really like to get in there and pull these springs. I tried a few quick ideas - put some WD40 in there, let it sit for 30 minutes, tried pulling/pushing/swearing, gentle taps on the wrench with a hammer, all to no avail. Anybody got any ideas? I'd really like to do this myself. I was thinking of using a torch to warm up the works but I'd like to hear from you folks first on potential fixes. I have a limited tool kit but not horrible. Really want to avoid a trip to the local mechanic...rather buy the tools as needed. Anybody have experience with this problem?

[20774]

WD-40 is not that great of a penetrant. Try either Aerokroil or PB Blaster. Sometimes it takes time...days instead of 30 minutes. A little heat like from a paint stripping gun could help expand things enough to let penetrant in deeper. I wouldn't go to a torch or flame device for heat...too much in my opinion.

That 36mm socket...did you machine off the end to get rid of the internal taper? Those fork nuts are thin and you need as much contact surface you can get. A 6-point socket would even be better. I had a tough time getting mine of a few years ago. I fired up my air compressor, used the 6-point socket (end ground down), and an impact wrench. It was enough to loosen the nuts. Something that can also vibrate it to help the penetrant to wick in a bit deeper. You could also use some valve grinding paste on the flats of the nut to help the socket grip better.

[azduc]

You can also tap firmly on the socket while applying pressure with a breaker bar, use a fiber or plastic type hammer, or even brass. Don't pound on it, just firm taps, you are trying to unseat the threads as you apply a turning force. Good luck!

[108625]

WD-40 is not that great of a penetrant. Try either Aerokroil or PB Blaster. Sometimes it takes time...days instead of 30 minutes. A little heat like from a paint stripping gun could help expand things enough to let penetrant in deeper. I wouldn't go to a torch or flame device for heat...too much in my opinion.

That 36mm socket...did you machine off the end to get rid of the internal taper? Those fork nuts are thin and you need as much contact surface you can get. A 6-point socket would even be better. I had a tough time getting mine of a few years ago. I fired up my air compressor, used the 6-point socket (end ground down), and an impact wrench. It was enough to loosen the nuts. Something that can also vibrate it to help the penetrant to wick in a bit deeper. You could also use some valve grinding paste on the flats of the nut to help the socket grip better.

Don't use a torch! Remember, your forks are full of air and oil in a confined space.
Use real penetrating oil overnight, and while you're waiting do yourself a favor and get a 36mm box end/open end combination wrench. It will apply a lot more leverage than than you can with a socket and ratchet, because it's not offset.
I installed the Progressives in my R100S a few years ago, they weren't difficult to install and it was well worth it. My fork gaitors hissed too, they just do it less now because there's less movement now with fresh springs in there.

Bob

[47512]

John, those nuts are tight, 120 nm, or 87 ft lbs. You want a socket that fits the nut very well, it is easy to damage the nuts. BMW calls them upper spring seats.
The std springs are 567mm, or 22.32" long, The RS springs are 543mm, or 21.38" long. There could be a spacer on the spring guide, you will see it when you remove the fork nut. The RS springs are alittle stiffer than the std. springs. They are alittle shorter to retain the same ride height. When you add or subtract spacers, changing the preload, this changes the ride height, it has nothing to do with the spring rate. Rule of thumb, you want about 25 to 30% of the total travel of the fork to be used when you sit on the bike when it's on it's wheels. More than that add a spacer. A dry fork will take 280cc of oil, if all you did was drain them add 265cc of oil as you cant get all of the oil out of the dampers. The OE spec oil was aero shell 4, it was simular to 5w. I like 7.5, or 10w if you want alittle more compression damping.

Ken G.

[JohnnyMoto68]

Great stuff, thanks VERY much for all the replies. I'm happy that I posted, since my idea for a torch seems to be overkill. Instead, here's the plan:

I do have a socket that's been milled, got it from Joe - link below for anyone interested, some other goodies on here too:
http://www.culayer.com/Joes_tools.htm

I can definitely see the logic in getting a 36mm box end/open end combination wrench and I'm gonna go that route next. I'll use the socket w my torque wrench when I put em back on. I'm also going to hunt down some PB Blaster or Kroil and let it soak for a while - maybe a few days at least. I have an air compressor but no air tools yet - might go with a basic impact wrench from Craftsman or something similar to keep the costs down. I have an older Ducati that's probably going to need some of the same 'frozen bolt' solutions, so it might just pay for itself in the long run. It's gonna be cheaper and more fun than having someone else do it.

It sure is nice to be hooked into such a great community of folks who are ready to give advice and experience. I really appreciate it. Thanks everybody, I'll let you know how it all works out, and hopefully can help the next rider with the same problem.

[20774]

I have an air compressor but no air tools yet - might go with a basic impact wrench from Craftsman or something similar to keep the costs down.

Take a look at Harbor Freight...they have some pretty decent air tools and the price is nice, too.

[rbryson]

I recently had Progressive Springs put in my 1976 R90/6 and regret doing it. After spending $400 on two different mechanics I wish I had left the originals in, as bouncy as they were. I put Progressives in and the front fork was so tight and firm that I thought small bumps at low speed were going to break the bike in two. Then I put BMW heavy duty springs (I have a Windjammer Fairing) but they were no better. Now the forks don't move much at all. The only way to get the forks to compress it to rock the bike back and forth with the front brake on. There is little or no rebound. I have to pull up on the handle bars to gets the forks to return to their starting place. Two different mechanics have spent hours working on it, but neither have been able to fix it properly. The original springs were 30+ years old, but at least when I hit a bump they would move up and down. Now I feel every thing unless I am riding the Interstate...so beware. My advice is not to take off the forks. Getting them realigned is much harder than others led me to believe. Really regret changing springs.
Rb

[ccolwell]

I've had stiffer springs, usually Progressive in all three of my airheads and never regretted it. You lose some comfort on bumps, but the increase in stability turning and braking is well worth it. With stiffer springs, I found 7.5 wt fork oil to be the best compromise between comfort and handling (and yes, I made it by mixing 5 and 10 wt). This shouldn't be a problem on your bike unless you have a CC Product upper triple clamp, but make sure there is nothing clamping the fork tube where the cap threads in -- that will prevent it from loosening.

[rbryson]

I agree the handling and braking are better. But, I would like to hear from others who have gone to Progressive or BMW Heavy Duty springs. In particular, do the forks compress and rebound from a stationary position, or are the springs so fixed that you have to pull up on the handlebars to get the forks to return to their normal position as I have to do in my garage. I am looking for a smoother ride with some improved handling and from what I had read the Progressive Springs were the answer. On my bike the rough ride at slow speed is not worth the improved handling in the curves. Am I alone in this assessment? I have tried different fork oil weights but none seem to make a difference.

[jforgo]

From Harbor freight has short handle open end wrenches in 1MM increments. The tiny handle fits perfect into the 2 piece jack handle from my Harbor Freight floor jack Use one hand to keep the wrench exactly on the top nuts - you get a lot of leverage, merely press jack handle, and presto - breaks it loose easily.

As to Progressives in the front, I just installed on my 82 RT, with 7w BelRay oil. Also did the San Jose BMW upper triple, which also changes the preload spacer calculation. I wound up using some hardware oddment from my garage to get the right spacer length. I had also replaced the rear shocks with Progressives. With all this done, I went out into our high crosswinds, along with the lovely bits of partially completed freeway construction. Thrown in are the usua deteriorated pavement on city streets and curves. This setup kept my tires to the ground at all times, no crosswind gust pogoing, rock steady tracking over horrid surfaces, etc. My RT is much more of a blitzkrieg machine. These conditions I think are the real test of suspension.

Based on procedures described in various threads, I suspect a lot of people disassemble bits unnecessarily for various front end work, and then bolt back up on an ad hoc basis, with no alignment attempted. I wonder if some of the Progressive fork spring complaints stem from stiction of misaligned fork bits.

This is not to say, of course, that some simply prefer a lightly damped, softer ride, which the setup such as mine definitely reduces. If you like the stock ride, there is no reason to modify the suspension.

[bikerfish1100]

I agree the handling and braking are better. But, I would like to hear from others who have gone to Progressive or BMW Heavy Duty springs. In particular, do the forks compress and rebound from a stationary position, or are the springs so fixed that you have to pull up on the handlebars to get the forks to return to their normal position as I have to do in my garage. I am looking for a smoother ride with some improved handling and from what I had read the Progressive Springs were the answer. On my bike the rough ride at slow speed is not worth the improved handling in the curves. Am I alone in this assessment? I have tried different fork oil weights but none seem to make a difference.

i put Progressives in my R100S, and my R100RS (both '78s). never had the issue you describe. Also ran Progressives in my K75C (with a Pichler) and my K1100RS, also no issue. I suspect that the problem is not with the Progressives- Unless you put in much too heavy of a spring rate for your bike- rather there is something likely amiss with your front end. good luck.

[rbryson]

Did you simply change the springs or did you remove the forks and then replace the springs? Wish I had just replaced the springs. Once the forks are removed it seems know one can get them back on straight.

[bikerfish1100]

I'm a little late on this, but I was interested in the difference - so I reviewed the photo gallery I've been assembling. Here's a merged photo of the two types of forks - in a 1982 R100 RS (Type I) and a 1996 R850 (Type II). FYI

http://www.hal4d.com/images/Fork-Comparison.jpg

isn't that an apples to oranges comparison? the R850 is a Telelever front end, correct? if so, it's front end has virtually nothing in common with any airhead front end, other than the front wheel and handlebars attach at either end of it.

[bikerfish1100]

Did you simply change the springs or did you remove the forks and then replace the springs? Wish I had just replaced the springs. Once the forks are removed it seems know one can get them back on straight.

for those jobs, i only replaced springs. But i have changed out fork tubes before, including on the RS with the Progressives, and like i said, never an issue as you described.

[bobh41]

Bikerfish1100 wrote:
isn't that an apples to oranges comparison? the R850 is a Telelever front end, correct? if so, it's front end has virtually nothing in common with any airhead front end, other than the front wheel and handlebars attach at either end of it.
__

My apologies for failing to pursue this fork question to it's ultimate (and correct) conclusion. I don't have hands-on experience with this, and will happily accept any corrections to my pursuit. You are right that the 850 is in a different model category than the airheads. My error - trying to "see" assembly differences in low resolution photographs (my model ignorance notwithstanding).

Reviewing the fork tube types in Clymer M502-3 (1970 - 1996), all airhead forks are called out as Type I through Type IV. Clymer M503-3 (1993-2005) identifies all forks by model type. And the R850 fork assembly is nothing like the airhead Type II.

Thank you Biker, for calling this out.

[ccolwell]

I recently had Progressive Springs put in my 1976 R90/6 and regret doing it. After spending $400 on two different mechanics I wish I had left the originals in, as bouncy as they were. I put Progressives in and the front fork was so tight and firm that I thought small bumps at low speed were going to break the bike in two. Then I put BMW heavy duty springs (I have a Windjammer Fairing) but they were no better. Now the forks don't move much at all. The only way to get the forks to compress it to rock the bike back and forth with the front brake on. There is little or no rebound. I have to pull up on the handle bars to gets the forks to return to their starting place. Two different mechanics have spent hours working on it, but neither have been able to fix it properly. The original springs were 30+ years old, but at least when I hit a bump they would move up and down. Now I feel every thing unless I am riding the Interstate...so beware. My advice is not to take off the forks. Getting them realigned is much harder than others led me to believe. Really regret changing springs.
Rb

I just looked at this again and it sounds to me like something else is wrong and preventing the forks from working properly. It could be a bent fork tube, but if nothing else happened except a change of fork springs, that seems unlikely. The forks could be badly misaligned -- try loosening everything on one side (lower triple tree bolts, fork brace/fender mount, axle) and tighten everything working from top to bottom, bouncing the fork up and down before and between tightening each component. If this doesn't help, repeat on the other side. If its too stiff and the fork doesn't return to full extension, there has to be something wrong.

[Isamemon]

progressives and a telefix fork brace were super improvements in my bike, 78 R80

as far as tools, another handi one is the hand impact screwdriver that you smack with a hammer, you can use it with sockets too. cost about 15 at my local auto parts stores. Ive gently used it to loosen those stubborn top cap nuts

[JohnnyMoto68]

My RT is much more of a blitzkrieg machine.
That's what I want. This machine isn't a cruiser - I want a dive bomber.

Ordered an impact wrench from Harbor Freight...waiting on delivery. Also picked up some other goodies. We'll see how they shake out. A lot cheaper than Craftsman, anyway. Hope I didn't just throw money down the tube - but ya gotta try everything once.

I'll post again when I get everything sorted. Glad I avoided my initial thought to use a torch.

[JohnnyMoto68]

Howdy. Thought I'd check in and report on progress.

I got some PB Blaster and soaked the top fork nuts for a few days, and used an air impact wrench that I got from H.F. Worked like a charm. I removed the springs and installed new Progressives, and have the factory spacers installed up top to test the initial performance. As reported other places, these springs are very, very stiff - riding in Brooklyn and Manhattan which is pothole central is pretty harsh. No worries, since I'd like to keep the bike for more distance oriented riding anyway.

At the same time, I still have my sound issue - whoosh whoosh when I hold the brake and push down up front. It just doesn't feel right. I need to perform more investigation, but I'm starting to think that I need to replace the fork seals. If that's the case, I'd probably go ahead and do the steering bearing as well...which inevitably means mechanic time.

Rather do it myself, but I'm worried about fork alignment - feels like a difficult task.

Any good fork rebuild kits for a 1977 R100S out there?

[BubbaZanetti]

I removed the springs and installed new Progressives, and have the factory spacers installed up top to test the initial performance. As reported other places, these springs are very, very stiff - riding in Brooklyn and Manhattan which is pothole central is pretty harsh.


we have the EXACT opposite problem, my springs are so bouncy and plush i keep whacking the front engine cover into the rear of the fender. we should meet up so i can use your socket and swap spacers. :thumb

[mymindsok]

I recently had Progressive Springs put in my 1976 R90/6 and regret doing it. After spending $400 on two different mechanics I wish I had left the originals in, as bouncy as they were. I put Progressives in and the front fork was so tight and firm that I thought small bumps at low speed were going to break the bike in two.

Uhm.... Did you try changing the shocks?

I agree that the progressives are stiff but I have also found that they arnt as big a PIA if the front and rear ends are matched. Stiff in front/stiff in back. My R-90HR is set up that way and everyone whos ridden it loves it!

OTOH, when I had fresh Progressives in front and old Koni's on the rear, it felt like every bump was the size of a meteor crater and the bike wasnt a pleasure to ride again untill the fork springs were half worn out.

Check the entire suspension before you blame the springs!