Shock assessment

[A100man]

I have a subscription to Practical Sportsbike it was a Xmas present from my (wealthy-ish)_ brother a couple of years back who has failed to cancel the direct debit.. I really ought to tell him..

Anyway, the point is they often add ride reports and reviews 80s 90s bike that have been restored. and invariably they will say. ' Great bike blah, blah if only Bob/Mike/Terry had replaced the worn out saggy shock(s) it would handle like a dream.. we recommend a new Nitron shock, blah blah custom built to suit ride, should only be 700 quid

.. this perplexes me as I'm pretty sure I'd find it hard to tell. I can bounce the rear end of my FZ lik ethe MOT guy does and the damping seems fine, it never bottoms out (OK so I'm only a lightweight) so is it OK? It has some preload adjustment but you'd be hard pushed to alter it on teh bike witout getting bloodied knuckles. But wtf is 'rebound adjustment'? extra damping?? How would I know when that is needed?,

Saying all that I have noted a shortcoming on my 550/600. It was sporting some of those cheap 'progressive' chinko shock until lately and they might as well have been steel rods as the ride appeared very harsh..
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[Riejufixing]

[stinkwheel]

Static sag is the main thing which is all down to the springs and how much "springiness" is left in them. Too much sag and they are saggy. Always start by setting your static sag.

The damping is the icing on the cake which determines how quickly that springiness comes into play. That's what prevents them "bouncing".

So it's a measurement of how far the shock compresses when you set the bike on its wheels from being supported off its wheels. If the bike is 25-30 years old, the spring will be shorter and less springy than it ought to be. Most of them had too much sag right out of the box anyway because they weren't designed for big heavy Westerners to sit on.

You can adjust static sag to an extent with the preload adjustment.

Then there is rider sag which is how much more they drop when you put the rider on, this is about spring rate/strength. Again, usually way less than it should be.

The normal procedure is to use a spring calculator tool to work out what spring rate you should have, set the static sag with the preload adjuster and the rider sag should be about right.

Then what happens is having fixed the shock, it highlights how shitty the fork springs are, so you replace the springs, sort out the damping and you now notice how crap the brakes are.

I know quite a few people who have had good experiences with chinese shocks. Not uncommon for club racers to use them. They sell them by extended length. Not usually quoting a spring rate but still usually better than the old tired ones that were fitted. I've got a set on my bullet that are going on 4 years old now. No complaints. Adjustable gas damping and a massive improvement on the originals. Cost me £80 delivered so can be worth a punt.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Bhud]

Are you talking about your Yamaha Diversion? If it's anything like mine was, the rear shock will be well and truly knackered by now. A new shock (or an old sports bike shock that still has some life in it) will make a world of difference. If I accelerated the bike as hard as possible from [not quite legal+ mph] on a country road where the tree roots were pushing up the tarmac, the rear wheel would slip. That was a shot shock. If you're buying a new one, the YSS ones are known to be good. If you search online, various sports bike shocks can also be substituted with greater or lesser success.

[chickenstrip]

I'm not great on knowledge of how to set suspension up - I suppose I'm just lazy, and haven't taken the time to learn about it. But I do know that when done properly, it can really transform the enjoyment of riding a bike, to the extent that if you don't know/can't be arsed to do it yourself, it is worth paying someone who knows what they are doing to sort it for you (up to a point!).

You really don't know what a bike's handling potential is until you have decent suspension, properly dialled in on it. And if it isn't, you're really wasting your bike - assuming you like to push things a bit on a nice twisty road. If you just like to bimble around, it's no big deal though, not worth throwing the time and money at - again, assumimg it's not dangerously bad. But when you do sort it properly, you may find yourself pushing it on a ride anyway, simply because it just copes with what you throw at it. I did this because on standard suspension, I was finding fault.

So on my current bike, the philosophy has been to spend a bit and let others who understand it all sort out the adjustment. It may be that things could be better still, but I'm happy with how it performs for my level of ability on a bike. I've had the pegs scraping without feeling on the ragged edge of control, and that's certainly good enough for me, and the ride generally is smooth, goes where I point it without drama. I did the conversion because with the standard suspension, I was finding fault. But if you're not feeling at all limited by how your suspension behaves, probably not worth the effort to play around, especially if you don't really know what you're doing.

Prompted by Bhud's comment - even a cheaper-end replacement shock is worth it if your standard item is knackered, from a performance point of view, though it might not last as well as the higher-end ones, which might also be rebuildable. On one of my last Fazers, I replaced the rear shock with a new Hagon item - it might not be at the level of Nitron and some others, but still better than the tired old standard job that was on there, and didn't break the bank.
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Chickenystripgeezer's Biking Life (Latest update 19/10/18) Belgium, France, Italy, Austria tour 2016 Picos de Europa, Pyrenees and French Alps tour 2017 Scotland Trip 1, now with BONUS FEATURE edit, 5/10/19, on page 2 Scotland Trip 2 Luxembourg, Black Forest, Switzerland, Vosges Trip 2017
THERE'S MILLIONS OF CHICKENSTRIPS OUT THERE!

[MarJay]

I bought a cheap Nitron for my VFR for £450. Then I set it up for my weight.

Honestly it IS that good. I'd suggest someone who can't tell the difference has no nerve endings. In fact I'm tempted to buy another couple for my other bikes. Definitely the street triple, maybe the CBR (although the CBR and the KR1S both have had shocks rebuilt for me).
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[wr6133]

I've found even the cheaper end of the market for shocks can be a massive improvement on older worn out stuff.

My current ZZR had 14k on it when I got it, the shock was crap from new but the miles and 14 years (at the time) had left it tired and saggy. No amount of adjusting and fiddling could get it right and when riding 2 up the slightest corner would sink it enough to grind the centre stand. £350(ish) on a YSS shock and the bike currently has smaller chicken strips than my GSXR.

They can go from being a bit "wooly" to throwing you down the road too. My prior ZZR around 80k miles, shock just bottomed out while riding and then stuck in position, spitting me down the road. Replaced that with a YSS as well, was like a new bike.

[chickenstrip]

[A100man]

[A100man]

Thanks all for the tips _ I'll take a look at 'sag' and see where that leads.
I'm built more like Jorge Lorenzo* than Michael Dunlop so bottoming out hasn't happened and I'd say I'm much more bimbler than racer.

* or how he might be in another 20 years
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Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600

[Bhud]

[chickenstrip]

[wr6133]

[A100man]

[wr6133]

[stinkwheel]

[A100man]

[wr6133]

[stinkwheel]

[Kawasaki Jimbo]

You need to think about what the front and rear are doing on bends, rather than how the suspension bounces or shields you from bumps. The summary in the link below has a nice little graphic.

https://www.gostar-racing.com/club/motorcycle_suspension_set-up.htm

Think about how the bike steers: tipping in, holding a line, exiting. Try to work out what front and rear are doing; are they diving/rising too fast or too slow, or not working together.

Find a half-mile stretch of road with a roundabout at each end and a parking spot along it to fiddle with suspension settings. I did this with the ZX6R and although there was no eureka sweet spot moment I do think it was improved. I was lucky insofar as the front seemed to be spot on. It can even be hard to work out whether it's the front or rear that needs a tweak, and any adjustment might well influence how the other end behaves. Record your starting settings.

My R1 could do with some adjustment to combat a tendency to run wide but I've ridden around the issue. The Kawasaki and the Yamaha have stock fronts but I've fitted Ohlins rears, eBayed and professionally rebuilt.

It's a bloody complicated topic! Interesting though.

[Bhud]

[stinkwheel]

[Pigeon]

[A100man]