Paging suspension gurus

I have a kind of problem with the Thunderace. If I'm cracking on a bit
and then need to use the brakes heavily I get the back end swaying all
over the shop. It's quite disconcerting when it happens and forces me to
back off the brakes to slow the swaying. Now the brakes on the Ace are
wonderful, stop on a sixpence jobs. I'd like to be able to make full use
of them but this is hindering me somewhat. In fact it frightens the ****
out of me, cos today I nearly hit two cars as I had to back off the
brakes on both occassions.

Ordinarily the bike handles well, if a little slow to turn in to some
corners and needs alot of effort to make it do quick changes of
direction on tight S bends. On fast sweepers it is sublime but at lower
speeds it feels a touch nervous. I still haven't mastered roundabouts on
it as it feels like it's going to slide away, even though I have bags of
confidence in the tyres.

Talking of tyres, they are Dunlop 207RR which are excellent in both feel
and condition, pressures are as recommended by Dunlop. All suspension
settings are as per factory. I have preload, compression and rebound
adjusters on both ends. Forks are straight with no leaks from seals and
rear shock still feels like there's some life left in it.

Wtf is the matter with it?

 

I'm no expert, but it sounds like the geometry is out somehow - like, too
high/hard at the back or too soft/shorter springs or spacers missing at the
front, and hard braking changes it further, from way out to fucking
dangerous. Is the back end unusually high, have the forks been raised up
through the yokes, was the previous owner enormously fat? Does it handle
better with a pillion?

First thing I'd do is make sure the suspension F and R is absolutely
standard.

 

IIRC it's still the original - now with, what, 40k miles on it?

 

That's a "yes", then?

 

I'm watching you, Richard William.

 

Colin Irvine says...

42K now. Still feels like there's plenty of damping though. Other than
this small thing I'm really very happy with the bike, especially now
I've welded the fairing back together and done all the paintwork.

 

platypus says...

Suspension is all bog-standard.

No and no

You'd have to ask Colin or Pat Irvine. I wouldn't like to say

Difficult to say. I rarely take pillions and they are inexperienced ones
when I do, so I take it relatively easy with them on board.

It is.

 

Champ says...

Thank you kindly, Sir. looks like tomorrow I'll be taking some light
tools for a ride-out to a favourite road of mine.

 

Lozzo wrote:
[snip tale of sussy woe>

Have you set up your sag to your weight?

This site may help

http://www.sportrider.com/tech/146_9508_tech/

also when was the last time you changed the oil in the forks, it would
be a pisser to fanny about with the fork settings just now only to then
change the oil and go through it all again.

 

Martian says...

No, I haven't changed a thing on the suspension settings, except put the
rear preload back to factory setting. Colin, who I bought the bike from,
is a little heavier than me and often rode long distances loaded with
gear and a petite pillion[1]

Excellent, thanks very much.

I haven't changed it, yet. I may do now. I have a feeling it may have
been done at the last service when the previous owner had it. It was
scheduled to be done at that mileage.

[1] That's put me in Pat's good books

 

Colin Irvine says...

You'd better polish up the new one, or you'll be wanting this one back

 

Heh. Looking forward to seeing it.

 

No, its a "no". I'm just a tad short for my weight.

 

You can never go back.

 

It was somewhere around Barstow, on the edge of the desert, when the

Wear in the swingarm?

--

Dave

GS 850 x2 / SE 6a
SbS#6 DIAABTCOD#16 APOSTLE#6 FUB#3
FUB KotL OSOS#12? UKRMMA#19 COSOC#10

 

Martian says...

All been checked and are in excellent condition. A small tweek of a few
settings and it handles lovely now

 

I would also recommend checking the rear suspension pivot linkage
bearings and bushes for play or maybe needing a lube job, unless of
course, you know they have been replaced recently and are moving freely.