"Lowering" an R-GS

[ultracyclist]

When you lower a GS, what are the trade offs? What do you give up? What is the big downside for doing that?

I have a 29 and one half inch inseam, and I must be on tip toes to be stopped on the bike.

[manicmechanic]

There are two ways to reduce the stretch to the ground. One is by fitting shorter shocks. I'm told that putting a set or RT shocks will do a good job. Or there's the aftermarket.

The other way is to get a custom saddle that lowers you, maybe sufficiently.

Or perhaps a combination of the two.

When you sat on my bike the other day, it was set up for my inseam. I've a buddy with a GS that is maybe your height and inseam. For him, using the stock shocks, the spring preload was reduced to minimum, and now he can flat-foot the bike. There are adjustments that can be made without resorting to the rack.

[ultracyclist]

Randy,
I had a feeling that you were going to respond to this one.
How were the brews?

[manicmechanic]

I'm getting acquainted with the Founders DB right now. I've been behaving myself and remained "fit for duty" while on-call, but I turned that over this morning. Next time you want to come up we can discuss suspension set-up, including static sag, riding sag, and the various dampings. How's the tool shopping going? Remember, you don't have to go out and buy anything yet. Think about it first.

[ultracyclist]

I definitely want to meet with you again. In addition to "sags", there are other things that I have questions about.

One thing I need to improve are the mirrors. The little convex stick ons are as distracting as they are useful.

I will get the minimum amount of tools.

Unfortunately, the next 10 days for me are nuts with family and business stuff.

[robsryder]

When you lower a GS, what are the trade offs? What do you give up? What is the big downside for doing that?

Last week I attended the seminar given by Tony Foale. Tony is the author of "Motorcycle Handling and Chassis Design" and is regarded as one of the subject matter experts on this topic. Tony has software capable of evaluating changes to a suspension system (such as lowering).

At the seminar several examples were used to illustrate the impact of even small changes to the rear suspension. In one instance I couldn't even see the change, but the impact on the overall operation of the suspension was quite dramatic (including on the negative side - locking the suspension!).

As a result of seeing the impact of these changes, I would not recommend that anyone make a suspension / chassis change without first undertaking a rigorous evaluation of the effect of the change. Such an evaluation could be performed using software such as Tony sells or through a similar mechanical evaluation. The full range of operation of the suspension system needs to be considered.

The website for Tony Foale is shown below:
http://www.tonyfoale.com/

[robsryder]

Another source to evaluate suspension change effects is "Motorcycle Dynamics 2nd ed" by Dr. Vittore Cossalter. This book is due out in July 2006, but I've not yet seen availability at Barnes & Noble or Amazon - I plan to get a copy when available.

An example of Dr. Cossalter's evaluation of suspension is shown for the BMW telever front suspension at the link below:
http://www.dinamoto.it/DINAMOTO/on-line%20papers/Telelever%20or%20forks/Telelever.html

Dr. Cossalter is part of an engineering group that evaluates motorcycle dynamics at the University of Padova in Italy. The cited link above is in English.