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Weight, Rates & Sag

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blacklines View Drop Down
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    Posted: 30 Jul 2018 at 10:02
As a completely normal warmup to packing my garage up for a house move I decided to measure and set my sag again. I last did this after swapping out my shock spring for a heavier one to get around my stiff at front/soft at back problem Shocked.

With the fork pre-load wound right out as soft as it would go I got 29mm free and 34mm static. With the shock pre-load down as tight as it'd go I got 8mm free and 39mm static.

I think the forks would be alright (although still slightly on the stiff side) if the shock was more like 10mm free and 26-30mm static. Also, unless they are that stiff stock I have no idea what their current rate is. Colin (?) at 100pc suspension said these Showas were known for having heavy stock springs.

I've already put in what I believe to be a 650 lb/in (11.6 kg/mm) shock spring. On the stock spring I was seeing about 50mm static sag!

I weigh about 100kg without my gear so heavy but not too much. I'm starting to wonder if the linkages aren't standard for the 2003 gen 1 or something.. I can't imagine finding a spring much heavier than an 115 Nm/mm.

Of those of you around my weight, what spring rates are you using and what sag numbers does this give?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 10:09
This is the shock spring I've got on. I spoke to Chris at K-Tech to confirm the 650 meant 650 lb/in (114 Nm/mm). Chris was adamant that it's actually 65 Nm/mm as they have always used metric.

I'm not sure what to believe because the spring is stiffer than the stock 95 Nm/mm and the only 65 Nm/mm K-techs I've seen have been -65, not -650.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 11:08
According to their parts list their springs are rated in N/mm and the stiffest spring they make is a 105 so yours can't be 114.
It's a 65 almost certainly (softest they do) which is why your getting big sag numbers. Mid 20's would be much more like it sag wise. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 11:24
Tempted to try a 105 I've seen on eBay.

65 doesn't make sense unless the bike came with a 45 though. My sag numbers improved by about 15 mm going from the stock one to this one. Previously was getting about 50mm with zero free sag. That's the other thing, this spring must be fractionally shorter because I still have 8mm free sag wound right in. 10 would be better but I wanted to reduce static as much as possible.

What spring rates are you using?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 11:29
The catalogue shows they do 57-160-115 although it's just listed for Ohlins S46. For ducati and Aprilia they only go up to 105 but I'd imagine that's just because it's outside recommended range for the bikes.

The lowest rate I can find on the catalogue is 85 Nm/mm although they might have gone lighter in the past, or maybe for offroad.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 12:14
This is the K tech parts list I looked at.
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Spoonz Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 12:17
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2018 at 13:06
Ah ok, thanks Spoonz.

I was looking on the UK site:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 07:05
You were right Spoonz. I fitted a ktech spring marked as 105Nm/mm and it was definitely a higher rate than the one marked 650. The 105 was marked up with 11.1 which I take to be the actual measured rate in kg/mm.


Shock(650 spring)

Full 565

Free 557 (8 mm static)

Static  526 (39 mm rider)


Shock(11.1 spring)

Full 542

Free 530 (10mm static)

Static  514 (28 mm rider)


Fork

Full 121

Free 92 (29 mm free)

Static 87 (34 mm rider)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 07:07
So I'm pretty happy with that. On a quick ride it felt much more balanced. Really dig into corners where before I always felt like I could lose the front from not having enough weight on it. 

If you weigh around 100kg it looks like the 105Nm/mm is the shock spring to have.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MSNracing Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 20:45
have just done my first track day on my 99 Rsv has an Öhlins rear shock but seems to be bottoming out and catching the undertray, we wound the spring down about 9 complete turns and although slightly better still catches, is it just a case of a better spring ? How easy/hard to do myself ? How do you know the right spring rating ? Thanks 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 21:07
I didn't know the right spring to be honest. I started with the stock one that is 95Nm/mm on the Sachs shock. Then I found a 105Nm/mm spring that is 2 sizes up which seemed to work.

On the stock spring I had the preload wound as tight as it would go and it still was too soft. I wasnt bottoming it though, i the weight balance was just too far rearward. It made the front end feel like it could wash out, particularly on corner exit. In fact the only time it felt ok was trail braking.

Ktech, maxton or any of the track suspension services will be able to help you get right spring rate of you're not sure. New springs are about £85 I think. I just went the cheap tourr of finding springs on eBay for £30. If you do this you are looking for 57mm internal diameter, 160mm length.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote legend88 Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 21:09
Is the shock/linkage original on the bike? Maybe one or the other came off another bike and the shock is the wrong length for the rear linkage? Has the shock ride height been altered?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 22:24
I'm not sure to be honest. The linkage looks original but I don't know if it came off another year RSV. I don't know the sizes of the different years so hard to say. The 105 has done the trick now though. Pretty much bang on sag and the bike handles much better.

I've got 4 threads showing on the shock for ride height. The forks have 3 rings showing but I'm thinking of dropping it to 4. Want to focus on making it good for the track really. I still ride on the road but take it easy so I don't mind sacrificing handling on the road for feel on the track.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 10 Sep 2018 at 22:32
Sorry me racing, yes it's a job you can do yourself. You'll need to support the bike somehow, either strap it to the roof of what I did was stick car axle stands under the rearsets. Take the back wheel off and belly tray for access. Then the shock is bolted on at the linkage at the bottom and at the top. Wind the preload right off and you should then be able to prise the spring down with a screwdriver to pop the top cap off. Spring then slides off the end. 

The hardest part of the job is getting the top bolt back in again. I don't think on all years but on the 2003 for sure there is a small recess in the plastic under seat tray that I think is to stop the bolt falling out if it came undone. This makes getting it back in a right pain. Need to wiggle shock and tap the bolt back in with a screwdriver and hammer. 

I don't think yoursy was bottoming on the plastic tray though. Look under there and you'll see there's no way for the shock to hit anything. There's not enough travel for the tyre to hit the under tray either. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote legend88 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 06:24
Originally posted by blacklines blacklines wrote:

I'm not sure to be honest. The linkage looks original but I don't know if it came off another year RSV.


Sorry, should have been clear, I was responding to MSNracing as his problems sound quite severe which suggested he may not have the correct items fitted.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 08:05
Ha yeah I did wonder after I sent it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MSNracing Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 19:02
thanks for advice, I can confirm it was the rear wheel hitting the undertray an scorching a couple of holes in it I wasn’t running a hugger. I’ve only just bought it as a track toy so I don’t know if there is another issue I should be looking for ? Spring is an Öhlins 1091-31/95 L090 so from what your saying this is stock and I need to look for a 31/105 ? Is there a chart any where? Thanks 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 21:38
Ohlins mark their springs in a weird way. I think the 31 is for 95 and you need 36 which is for 105. Saying that, you don't have to get an ohlins  branded spring.

There should be a better chart but this is the first I found:


Also, it's hard to say what spring rate you might need without knowing your sag measurements. How much do you weigh?

Like legend said, your problem sounds so severe there might be a funny sized linkage on your bike. I had grief with mine being inbalanced but there's no way I could bottom out like that. The bump stop on the shock was a bit shagged though..

Can you measure the free and static sag as a starting point? 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MSNracing Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 22:03
that’s possibly the best spring chart I’ve seen yet 👍 so with out sounding too dumb how do I measure sag & static ? 😬
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MSNracing Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 22:08
how do you use the spring rate chart in terms of weight of rider ? I’m about 118kg in my gear no there not lead boots I’m just a little comfy around the waist lol 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote damo46 Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 22:10
search on you tube for "setting motorcycle sag", Dave Moss videos are very good, I think
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CarsOrBikes Quote  Post ReplyReply Direct Link To This Post Posted: 11 Sep 2018 at 23:35
My interpretation has always been you only have to stand the bike on it's own weight ideally with a full tank and take those static sag measurements, which should be rear 0-5mm front 20-25mm ideally, then with your gear on get on the bike in your riding position with someone assisting balance if required, and note these positions, ideally rear 20-25mm and front 35-40mm, these numbers are from fully extended.

If you have higher rider sag you could use a next spring up, and with less, the next softer.

I tend to wind off all compression and rebound, and make sure the rear dog bone is free.

In one of the posts above, something that seemed odd, is that there was greater sag with a firmer spring, which would imply an error somewhere.

fwiw, I'm 6.3 15,5 stone, and have run all of my Factory's with OEM Ohlins springs, .95 and I tend to add a turn of rear preload, and remove a turn up front, if running a 190/55 instead of a 180/55 it can shift the balance, as can lowering the front yoke. I would only change one thing at a time. If it feels unbalanced it's easier to try to correct it at the front with trying different settings, but ultimately you may have to get springs.

That's how I've been doing it anyway, for years. I only had one bike with Showa and didn't get into it on that as it was only to sell, as with this current Factory, I'm setting it up, but only to the book for sale.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2018 at 10:25
Originally posted by MSNracing MSNracing wrote:

that’s possibly the best spring chart I’ve seen yet 👍 so with out sounding too dumb how do I measure sag & static ? 😬


There's lots on the internet explaining probably better than I can. This one is ok: https://www.therevcounter.co.uk/threads/34103-Motorbike-Motorcycle-Suspension-Setup

Basically you may need 2 people but the idea is to measure the distance from say your rear axle (or the slot your axle goes into works well) and a fixed point on your rear fairing. It doesn't matter a huge amount where, so long as it is a vertical line from your axle upwards. Measure the following:
  1. Fully extended: tilt bike on sidestand so rear wheel is unweighted and if possible off the ground.
  2. Bike self weight: balance your bike upright so the shock is compressed by only the weight of the bike on its own.
  3. Bike + rider: get on the bike and sit in a typical riding position. This will take a little weight off the shock compared to sat upright.
There's confusion over whether static sag is the bike on it's own or the bike + rider which is annoying.

Static/Free sag = Fully extended - Bike self weight
Static/Rider sag = Fully extended - Bike + rider

You always want around 10mm free sag to avoid being what Dave Moss calls the "second kid on a trampoline". I.e. with no free sag it can rebound up and shoot you out the seat.

Particularly on track you want the rider sag to be about 25-30mm.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2018 at 10:28
Originally posted by MSNracing MSNracing wrote:

how do you use the spring rate chart in terms of weight of rider ? I’m about 118kg in my gear no there not lead boots I’m just a little comfy around the waist lol 


I haven't found a spring rate chart for the Mille but there's always trial and error. 105 is just about bang on for me at 100kg with not too much preload left. If I were you I'd be looking for 110 or 115 if possible. 105 might be ok for really smooth tracks but probably borderline for you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 12 Sep 2018 at 10:34
Originally posted by CarsOrBikes CarsOrBikes wrote:


In one of the posts above, something that seemed odd, is that there was greater sag with a firmer spring, which would imply an error somewhere.


That was me going from the stock (95) to what I thought was a 115. It gave me less sag than stock, but not by as much as I thought. Spoonz told me the spring that gave less sag was actually a 65.

I replaced it with a 105 and had less sag still so the spring I had marked 650 wasn't 650lbs/in or 65Nm/mm. It must be somewhere between 95 and 105. Maybe 100. The writing looks different to other Ktech springs I've seen so maybe it's been printed with the wrong rate..
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MSNracing Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2018 at 21:05
so is there a recommended place to buy spares to refurbish the rear shock if I do it my self ? C spanner, preload rings, oil, spring etc ? Fed up of ringing my local Öhlins dealer and getting nowhere and k-tech website seems to be about as useful too ? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blacklines Quote  Post ReplyReply Direct Link To This Post Posted: 13 Sep 2018 at 21:17
eBay is my go to normally. Doesn't have to be ohlins stuff really, just anything compatible. I take it if you don't have c spanners then you haven't tried adding preload to your shock? To be honest I'd be surprised if the current spring would work for you anyway.

Why not start by gettign some c spanners. Wind down the pre-load and check your sag. Then look out for a shock spring to replace yours. If you email ktech themselves they should be able to help but obviously they probably won't be happy telling you what spring rate you need unless you're going to buy a spring from them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CarsOrBikes Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep 2018 at 12:38
I used Harris to renew a couple of shock parts someone messed up, all straightforward.
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