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Thread: Request for Pictures - Tire Rim Profiles

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    Administrator 20774's Avatar
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    Request for Pictures - Tire Rim Profiles

    I'd like for people to take really good pictures of their rims when there's an opportunity say at the next tire change...or if they have a bare rim sitting around. I'm really interested to see the profile shapes of the Snowflake rim versus the spoke rim of the day. I can't say as I've ever seen a Snowflake rim in person...all I have are the stock spokes on my /7. I know there are more rims types out there...Lester's, the Y-spokes mags, etc. Might be a good idea to have good shots of all of these...could be interesting!
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    I'd like for people to take really good pictures of their rims when there's an opportunity say at the next tire change...or if they have a bare rim sitting around. I'm really interested to see the profile shapes of the Snowflake rim versus the spoke rim of the day. I can't say as I've ever seen a Snowflake rim in person...all I have are the stock spokes on my /7. I know there are more rims types out there...Lester's, the Y-spokes mags, etc. Might be a good idea to have good shots of all of these...could be interesting!
    Here are a couple of pics of my 19" front snowflake.

    If I did it correctly, you should get 3 pics in medium resolution for better clarity.
    Attached Images Attached Images

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    Administrator 20774's Avatar
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    Jimmy -

    I'm really interested in the bead area, the flat spots on either side of the drop center...in the first picture it's pretty fuzzy. Also, if you had a small flat surface you could put across the bead area, it would help emphasize the slope that is supposed to be there...it should be a 5 degree up slope.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    Jimmy -

    I'm really interested in the bead area, the flat spots on either side of the drop center...in the first picture it's pretty fuzzy. Also, if you had a small flat surface you could put across the bead area, it would help emphasize the slope that is supposed to be there...it should be a 5 degree up slope.
    I have a pretty good camera, and I had a hard time getting it to auto-focus on that "edge".

    I will try again, and do a manual focus - taking various shots, and then upload the best one!

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    Outlander Omega Man's Avatar
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    Quote Originally Posted by 20774 View Post
    ..in the first picture it's pretty fuzzy.
    I think it's the "busy" background that is fouling up the view in the first picture Kurt.
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    Quote Originally Posted by Omega Man View Post
    I think it's the "busy" background that is fouling up the view in the first picture Kurt.
    OM
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    Try these.

    I decided to focus in on just one side, then the other since the sides are symmetrical.

    I also put up a straightedge and a machinist's scale so you can make some judgement as to size. I also inserted a black background.
    Attached Images Attached Images

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    Jimmy -

    That profile seems to suggest there is a slope going from the outside of the bead towards the center...it looks like the inside edge of the flat portion is higher than the outside. Is that what you see in person? That's contrary to the standard 5 degree angle for the typical tubeless rim where the slope is the opposite direction.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    Jimmy -

    That profile seems to suggest there is a slope going from the outside of the bead towards the center...it looks like the inside edge of the flat portion is higher than the outside. Is that what you see in person? That's contrary to the standard 5 degree angle for the typical tubeless rim where the slope is the opposite direction.
    In hadn't noticed what you are describing until you mention it now. At first, I thought it was simply a photographic illusion. But, I went out to the garage and found a machinist straightedge that would fit across there and you perceive it correctly. That "flat" really isn't flat, but is slightly higher towards the middle of the wheel. I am not sure (and don't have any way here to really measure), but I doubt that it is 5 Deg., but looks less than that. However is does taper down as it goes out toward the edge of the wheel.

    Hmmmm. Sharp eye!

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    Quote Originally Posted by 20774 View Post
    Jimmy -

    That profile seems to suggest there is a slope going from the outside of the bead towards the center...it looks like the inside edge of the flat portion is higher than the outside. Is that what you see in person? That's contrary to the standard 5 degree angle for the typical tubeless rim where the slope is the opposite direction.
    I hate to state the obvious, but

    1) Some people run them that way, but the snowflake is not a "proper" tubeless rim.

    2) Tubeless rims do slope "up" from the bead to the center. That is what creates the "pop" on bead seating and is why bead breaking more difficult with a tubeless tire on removal. It is the bead retention feature.

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    Registered User melville's Avatar
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    Maybe not the best angle:



    Pretty sure this is the 18" rear from my /6 when I was tensioning and truing it during the rebuild.

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    Quote Originally Posted by beemerphile View Post
    2) Tubeless rims do slope "up" from the bead to the center. That is what creates the "pop" on bead seating and is why bead breaking more difficult with a tubeless tire on removal. It is the bead retention feature.
    From what I've read, common tubeless rims slope "down" from the bead to the center. It was stated that this type of slope helps retain the bead because of the extra pressure put on the bead of the tire. One of the profiles I've seen of a tubeless rim is a "nub" near the center which would keep the tire bead from moving inward.

    So, we're seeing a different design in the snowflake rim. My guess is that the reverse slope on the snowflake would help keep the tire bead from migrating to the drop center, thus also a bead retention feature as you suggest. Once the bead drops into the center, the tire can more easily come off the rim...except that BMW used the a number of bumps in the drop center of their spoke rims to provide for some bead retention. Actually, these bumps are something that has to be dealt with when mounting a tire...the opposite side of the drop center is where you put the tire bead in order help the bead clear the rim on installation.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    From what I've read, common tubeless rims slope "down" from the bead to the center. It was stated that this type of slope helps retain the bead because of the extra pressure put on the bead of the tire. One of the profiles I've seen of a tubeless rim is a "nub" near the center which would keep the tire bead from moving inward.

    So, we're seeing a different design in the snowflake rim. My guess is that the reverse slope on the snowflake would help keep the tire bead from migrating to the drop center, thus also a bead retention feature as you suggest. Once the bead drops into the center, the tire can more easily come off the rim...except that BMW used the a number of bumps in the drop center of their spoke rims to provide for some bead retention. Actually, these bumps are something that has to be dealt with when mounting a tire...the opposite side of the drop center is where you put the tire bead in order help the bead clear the rim on installation.
    If my rear snowflake (4.00-18) is the same configuration/profile as the pictured front above, that would definitely make a tubeless tire (Like the Pilot Activ) much more difficult to install, though not impossible as testimonies right here have stated. I guess my situation was unique. I have no proof, but I would guess that all tires made as "tubeless" are also very highly monitored for quality AND are made to very tight specs (probably tighter than the tube-type tires of the vintage era.)

    When I purchased my bike last winter it had Dunlop non-period size tires. One thing (besides testimonies and also tread type) was the fact that Michelin Pilot Activ's come in period era size. So, when I couldn't get the Pilot Activ on the rear, I had to settle for Dunlop "Vindage" tire that was also sold with period era size. However it also has the period type tread which is probably not going to wear well on interstate/pavement roads as the tread is very coarse.

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    Quote Originally Posted by jimmylee View Post
    If my rear snowflake (4.00-18) is the same configuration/profile as the pictured front above, that would definitely make a tubeless tire (Like the Pilot Activ) much more difficult to install
    What's your rationale for that? If we call bead seating as having the air inside the tire push the tire bead outward up against the outside vertical part of the rim, then it would seem with the down slope from the center towards the outside as helping to seat the tire. If the slope were the other way as what appears to be the typical tubeless rim profile, that would mean that the rubber rim of the tire has to work "uphill" to seat...seems harder to me.

    Whenever I've thought about a tire bead seating, I would think about just the vertical part of the rim. But in reality, the rubber part of the tire has to work outwards along the relatively flat portion of the rim. If that's dirty or there's not enough lubricant, it could get stuck.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Quote Originally Posted by 20774 View Post
    What's your rationale for that? If we call bead seating as having the air inside the tire push the tire bead outward up against the outside vertical part of the rim, then it would seem with the down slope from the center towards the outside as helping to seat the tire. If the slope were the other way as what appears to be the typical tubeless rim profile, that would mean that the rubber rim of the tire has to work "uphill" to seat...seems harder to me.

    Whenever I've thought about a tire bead seating, I would think about just the vertical part of the rim. But in reality, the rubber part of the tire has to work outwards along the relatively flat portion of the rim. If that's dirty or there's not enough lubricant, it could get stuck.
    My rationale is that the tire bead has to get "over" that slight hump to then "seat" on the bottom and side of the rim. I remember studying the profile of the tire when I was having my problems, and I noticed that the TIRE profile was more suited to the profile of the 5 Deg. slope upward to the outside of the rim as opposed to the downward slope of my pictured snowflake.

    I can also see how the tubeless tire profile and the "tubeless" rim profile are designed to work together to get the tire to "capture" air at first filling allowing the tire to seal enough to allow the full pressure to "seat" the tire. I also, can see because of the "downward-toward-the-middle" would allow a tubeless tire on a tubeless rim to "unseat" quickly which is why they added the "inside" bead into the rim profile to help force the tubeless tire bead NOT to crepe into the middle of the rim during pressure loss - providing more safety in case of a puncture.

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