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+--- Thread: Rear Suspension for drag racing (/showthread.php?tid=1495)
Rear Suspension for drag racing - BEAR - 17-10-2006
OK all you experienced guys. I have slammed the Busa, and now have around 40mm clearance under the undertail.
That seems a bit marginal to me given that maybe 100% of the bikes weight (plus my lard) can be on the back wheel during a fang. So the chances are a bit of undertail may get worn away.
One solution is to raise the bike again, another is to remove the undertail or cut a hole, and the third is to play with the spring! Rasing the preload seems a reasonable approach, and I was wondering if anyone has done that, and therefore knows what preload is required?
Presumably you'd want the bike to settle just a bee's dick when the rider has sat on it so it has some suspension movement, but how much does the back compress under a wheelie condition? <i></i>
Re: Rear Suspension for drag racing - simmo - 19-10-2006
Arr you must have one of those fast Copper ones
When I lowered the rear of mine it took a few goes to get to as low as possible with out ripping out the under tail
I just lower it for the drags and stiffen up all the setting to get there and back
Cheers Robert
Aren't all Busas Copper & Plated, the others are just all very poor slow ugly copies !!!!!<i></i>
Re: Rear Suspension for drag racing - BEAR - 19-10-2006
Thanks Simmo. I bought a C spanner and raised the pre load by 1. 7 turns. It seemed fine, but hard to tell just how much clearance is left.
I took down a screw driver but never got around to playing with damping. Next time I will screw in compression damping to the max and see what it does. We had a few complaining of wheel spin last night, so I guessed leaving it a bit soft may help under those conditions. For the front I will try screwing in the rebound and see if that helps.
Cheers <i></i>
Re: Rear Suspension for drag racing - simmo - 19-10-2006
I don't touch the front at all, if your keen 50 psi in the front tyre
I Just adjust it up very hard to get there , then back it off the other way fully when I get there so it drops down fast and slowly come up
I tryed 20 psi in the rear tyre last night, any lower it may spin it off the rim I think, 20 seemed real soft
Cheers Robert
Aren't all Busas Copper & Plated, the others are just all very poor slow ugly copies !!!!!<i></i>
Re: Rear Suspension for drag racing - BEAR - 20-10-2006
That all makes sense. I'll try that.
Tyre pressures I think can go much lower than what most guys seem to run here. They stick around 32 PSI. But on the track they run slicks down to 28 PSI and that would be far tougher as the side walls take a pounding during cornering. On the track I guess spinning the tyre on the rim is the worse you can do, or maybe some instability in a straight line, but I'm assuming at 20 you still tracked straight?
For the hell of it, tonight I've been adjusting and measuring the preload at the back to see what could be done. If you take off the under belly fairing, you can maybe get the back down another 20 to 30 mm but then you'd have to preload it to stop it grinding through the undertail. One turn of the preload gave me a 2mm change when I sat on the pillion seat, and after playing around I figured it at around 2.3 Kg/mm at the wheel. INow I just have to see if I can play around and work out what preload I'd need to restrict the wheel movement to say 10 to 20mm during a wheelie. I suspect you'd need a stiffer spring because there doesn't seem to be a lot of thread to play with. Still keeps me away from the tellie!
Now, why can't my Copper Silver go as fast? I think I cracked 140 Mph last year 139 so far this year. <i></i>
Brock on Suspension for Drag Racing - aBUSa - 20-10-2006
www.brocksperformance.com/tech_suspension
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