Sprint ST FAQ's - Suspension

The personal views of BRG, November 2000.

LEGAL NOTICE - some or all of this article may be fictional. No liability is accepted for any use or interpretation of the material herein contained.

1. Bike

Stock, 2000-registered (DOM June 1999) Sprint ST in British Racing Green with BT57 front & rear. Fitted with top rack and box.
Author: 102kg (ready to ride) and 1.88m.

2. Intended use

When I ride solo, which is most of the time, I often ride quickly, using maximum acceleration, cornering and braking, and the full speed potential of the bike. I also regularly (though not frequently) ride with a pillion who doesn't enjoy the 'exciting' life (these are the times when I get 58 (UK) mpg). When I want to ride at my absolute limit, I use someone else's hardware on the track (i.e. Ducati 748 & 996 at Cadwell & Honda CBR600F at Donington). Ergo, I chose the ST as the best compromise fit to my contrasting needs.

3. Symptoms


4. Cure

5. Result

The change to the bike's handling has been quite dramatic. Looking back, my attempts to get the standard suspension to behave resulted in too much preload for the damping to handle. This gave a jarringly hard system, that pogoed like mad once the suspension started to travel. The new system, by comparison, is a lot softer, but remains controlled. It feels as if the wheels are staying planted to the ground, rather than skipping over the bumps.

A couple of hundred miles after the suspension mods, I felt I couldn't live with the stock BT57s and changed to Avon Azaro Sport AV39 front and Azaro AV36 (R). Unfortunately, this means that I had little opportunity to assess the suspension changes in isolation. Consequently, much of what follows is a result of the combination of suspension mods and tyre changes.

A while ago, I attended a talk by Avon's chief tester, Leo Smith, who impressed me with the design and quality of the company's products. This view was reinforced by the results of the MCN Tyre Test (see the Tyres FAQ). Avon also has a local factory, so I admit to a bit of bias.

I spoke with Avon about my lack of confidence with the BT57/old suspension front end, and they recommended using the Azaro Sport AV39 on the front instead of the Azaro AV35, as this would offer quicker steering and more grip. I thought I'd proceed with this recommendation despite the forebodings of Martin Fay/Howlin Dawg, and have reached a different conclusion - see below...

I can't offer much objective comment about wet performance of the Avons. Most of the roads I ride have such a large amount of diesel, mud, cowshit, smooth steel manhole covers and disintegrating tarmac, that I'm loath to experiment. The best I can say is that I don't find them any worse than any other tyre I've ridden in the wet.

On the road

The new suspension provides more control over the bumps, and the benefits of this become more apparent as the speed increases. There is very much less pitching at high speed in a straight line, and the added stability in cornering means that the bike stays on line and doesn't try to send you to the outside of the bend all the time. The quicker steering means that the effort required to turn is a lot less, and the improved attitude of the bike means that exuberant cornering is a lot easier.

For those of you that think that suspension mods are only for the speed freaks, consider the following: I often go for 4-hour rides 2-up at UK legal speeds. Although I have experimented increasing the preload for these occasions, my wife's back has decided that we'd leave it at the solo setting. The new set-up means that we can ride with a comparatively low preload (and hence easy on the vertebrae), and still the bike feels controlled. I have noticed that I put a lot less effort into steering; my wrists - which were quite painful after a long trip - are now relatively comfortable.

On the track

I realise that most people want an ST for more touring-related performance, but a sport tourer should also be able to hold its head up in the sports arena too.

Wolfram (my ST) and I took part in a track day in May 2001 at Darley Moor in Derbyshire UK. This course is basically a 1.5 mile triangle with two second-gear corners (50-60 mph), two sets of 100 mph+ esses, a 25-30 mph hairpin (in 2nd gear for ease of throttle control) and a half-mile back straight allowing 135-140 mph. The circuit was smooth and flat, and in excellent condition. The day was dry, sunny and air temperature about 20ºC. Track periods were 15 minutes on, 15 minutes off, and I used standard tyre pressures (36/42 psi).

I was able to corner on the limit, hanging my 100 kg frame well into the corners, consistently and smoothly scraping the pegs and my knee slider. The bike steered quickly and effortlessly into the bends, and through the esses (with a nudge of countersteer). The tyres were completely confidence-inspiring at turning point, apexing and driving out of corners. The plot was also stable during acceleration, high speed and braking - there was no need for a steering damper. The standard brake pads provided excellent bite, though a tad spongy. The gearbox, however, sucks! I'd give it an 25% chance of finding a false neutral during clutchless changes on the limiter! (It may be me, but I don't have this problem on a Ducati 996 or a CBR600!)

In short, the suspension and tyre modifications have resulted in a bike that is currently the match of my riding ability and understanding of what the suspension's doing. I'm happy that the (considerable) outlay has been worthwhile.

6. Feedback

Any comments/correspondence gratefully received: keith@headway-ltd.com BRG