Had a bit of a slap on Saturday on the A40, going pretty fast on a very slight right hand bend, acclerating hard over an undulating surface and the bars waggled harder than ever before. (Turning right out of Huenden Triumph if anybody knows it, say half a mile from the showroom heading back to London) Wasn’t quite lock to lock but not far off, pushed my hands off the bars.
My bike doesn’t have a steering damper and the bars are always a bit lively, just got used to it but this was much harder than it’s ever happened before, was going to ignore it but thought I’d ask if making the rear suspension a bit harder would help ? When the tyres were worn it hardly happened at all but now with new tyres it’s back to full force.
I’m guessing the bars waggle more with weight transfer to the back of the bike, if I add a bit of pre-load to the rear spring that will push the weight forward a bit - will that help ?
I think the correct answer might be a new spring matched to my weight rather than the stock one which is probably designed for a 45Kg Japanese test rider.
Bit of name dropping. Alf Hagan once told me (at a grass track meet) that most of the problems with the front end of a bike are problems with the back end. “Get the back end right first” was his advice.
Unfortunately, he never explained how you did that, but if he was right, I think your looking in the right area.
getting correct shock for weight sounds about right were not all stick insects so those of a “larger” frame probably give the rear shock a harder time, PM brian of race science on here see what he suggests, it might be summat simple let us know the outcome mate
you sure it hasnt got a damper?..curtis told me his 675 didnt have a damper… it did!
you are talking about your ZX6-R?..
my SV is very twitchy with the power on, hit a bump and you will know about it, i had one big TS at 90+, was lucky to stay on the bike, scary moments:w00t:
i had my suspension adjusted by B, it helped but it still shakes its head over bumps and that, i had it ‘shimmy’ at 120+ teh other day:w00t: loads of fun!
Cheers, yep, will have a chat with B and I think the problem is the rear end, from what I’ve read. Thanks Oldman, I heard somebody else make a similar comment recently.
Ratty, definately doesn’t have a steering damper, my gixer does, hidden at the bottom of the head stock and that doesn’t shimmy at all but steers much slower than the ZX6.
I wonder if the rear spring is not just too soft anyway but also after 20k miles a bit worn as in compressed a bit ?
I reckon you need a new rear shock Steve - the consensus seems to be that shocks tend to go off after about 10k - and although this will not be an issue when riding moderately - if you are pushing the envelope a bit the deficiencies in your rear shock will start to magnify greatly - resulting in difficulty in holding a line on bumpy surfaces and tank slappers under hard acceleration on uneven surfaces. (I know you know this!!!)
I was riding my ZX7R (20k on original shock) on a fast sweeping but bumpy country B road last night and I found it impossible to plot and hold a decent line through the bends at speed - i’m gonna replacethe rear shock in the winter and see if things have improved next spring (gettit!).
that is odd slarty, i would have thought it would have, maybe think about getting one, i want one for my SV, thing is i may upgrade my bike before i gt round to getting it.
suspension adjustment is worth trying, specially on a sports bike, it will more than likley omprove things and make it less twitchy.
Steve, the Busa has a damper. I use it as a guage, when I get a shimmy going on I know it’s time to back off a tad maybe time for a relaxing Cocoa and resume play later with less vigor
Before you throw money at your bike Steve, check the wheel and steering head bearings for any play.
If they are tip top then you need to think about your ride height. Tank slappers are usually caused (if not by worn bearings) by too much weight on the back and not enough over the front.
Historically its always been my skinny mates who have suffered with bar wobble than us fat blokes. There are lots of things you can try before spending £££s on a new spring/shock
Thanks for the suggestions, have pm’d B too, see what he suggests. Might wind up the pre-load on the rear shock anyway as it does feel softer than it did originally so might be compressing more.
rather than the stock one which is probably designed for a 45Kg Japanese test rider.
it did!
maybe time for a relaxing Cocoa and resume play later with less vigor 