Suspension Guru required!

Originally Posted by SV650Racer

Of course spring rate matters. BUT you cant postively tell correct spring rate from just measuring rider sag. Ok it gives you a ball park but you dont ride the bike sitting stationary on it. This particulary applies to race applications.

If you set my supersport bike using just rider sag it would show me i require a .8kg spring whereas my perfect setup in terms of my pace, riding style and general bike chassis setup requires a .9kg spring.

Ohlins work with their non ttx shock on a 8-12mm static sag range whereas the TTX works to a greater 10-18mm range.

Im not the techy geek here, this is only what ive learnt watching Steve work for the past six years. So excuse my lack of technical terms!..

Aye, I can see where it works. I think its probably a better track application when you do indeed have the right spring rate. So fair enough there Suppose that means ill have to check my static sag, as I have the right spring rate in there

By using rider on the bike sag I mean to say that you do make up a little for the spring rate being off, which would work better for a road bike where the spring is very likely to be wrong...

Trouble is we see alot for the road is when a rider comes in suggesting the spring rate is wrong, unless they are either end of the weight scale its often more just plainly down to a poorly setup bike overall or the fact the shock isnt working quite as it should.

Setting up especially spring rates is often a massive compromise for the road.

Originally Posted by SV650Racer

Trouble is we see alot for the road is when a rider comes in suggesting the spring rate is wrong, unless they are either end of the weight scale its often more just plainly down to a poorly setup bike overall or the fact the shock isnt working quite as it should.

Setting up especially spring rates is often a massive compromise for the road.

Aye, fair enough there

Does your shop by any chance rebuild Penske race shocks?

Originally Posted by ThEGr33k

Aye, fair enough there

Does your shop by any chance rebuild Penske race shocks?

Yes we can

Originally Posted by SV650Racer

Yes we can

Cool, ill certainly ask you (for a price at least ) then when it comes to the time

[yorkie_chris]

Gr33k, you not fancy doing it yourself?

Re. spring rates and stuff, surely the spring rate is the deciding factor in whether you can get the ratio of static sag and rider sag correct?

Originally Posted by Peter Verdone

Spring Rate OK - Both free and rider sag within acceptable range.
Spring Rate too soft - Rider Sag OK, but too little or no Free Sag
Spring Rate too firm - Rider Sag OK, but too much Free Sag

Then again, I can see that with very stiff setups on a front-biased bike like a 600 that it would be hard to accurately set and measure bike sag.

Originally Posted by yorkie_chris

Gr33k, you not fancy doing it yourself?

I suppose I could. But getting it re gassed may prove a problem. Mostly because I dont know where I could get it done.

Not to worry, I got a few more miles before that

I need it de-gassed not regassed The hydraulics shouldn't have any air in it.

I'd also argue that rider sag is more important that static sag as bikes don't ride themselves.

Given the choice (which I have been with my Bimota) I set the correct rider sag even though the static sag was non existant. The tail unit is too light to get any sag.

Any disparity between what rider and static sag should be and are, tells you whether the spring rate is right.

If static sag is OK and rider sag is too high (large) then the spring rate is too low. If the static sag is ok and rider sag is too low (small), then the spring rate is too high. This is where static sag is useful. But in the real world it's rider sag that should be set correctly if you have to choose between the two due to incorrect spring rate.


C

If you have no static sag then your shock will top out as soon as it extends, ie under hard braking and will then lift the rear wheel off the floor hence causing chatter under braking.

Ask how many race teams measure rider sag!. Spring rate isnt 100% down to rider weight. Overall bike geometry, rider pace and style all are just as important.

Originally Posted by SV650Racer

If you have no static sag then your shock will top out as soon as it extends, ie under hard braking and will then lift the rear wheel off the floor hence causing chatter under braking.

Ask how many race teams measure rider sag!. Spring rate isnt 100% down to rider weight. Overall bike geometry, rider pace and style all are just as important.

But to be fair, surely anything will top out with the weight of the wheel and swing arm pulling it down and nothing to push it back. Id guess how hardh to top out depends on rebound damping.