View Full Version : Initial suspension setup - help
Hi all,
Any suspension specialists out there :D
Just prepping my K3 race bike, come to ride it for the first time today with clip-ons and its awful. Anything other that dead straight and the bars feel like they want to tip in very strongly to full lock.
It had wide bars when I got it and it was styled as a streetfighter so my guess is that the rear end may be way too high. The forks are set correctly as per the manual so they are not high in the yolks. I have nothing to compare it to though.
Two things I thought of, the rear dog bones may be none standard length. The ones on it are approx 150mm between centers.
The rear shock is from a GSXR1000 and came with the bike, looks like the preload is set pretty tight.
Any ideas?
Because there's so many variables and we can't try the bike, it might be worth starting right from the beginning.
This is a really useful guide:
http://www.gostar-racing.com/club/motorcycle_suspension_set-up.htm
Cheers,
Carl
Because there's so many variables and we can't try the bike, it might be worth starting right from the beginning.
This is a really useful guide:
http://www.gostar-racing.com/club/motorcycle_suspension_set-up.htm
Cheers,
Carl
Ok thanks, will do. Can anybody help with regard to the geometry of what it 'should' be at the rear though, maybe the shock is too long, maybe the doglegs have been replaced etc. I really wanted to get some confirmation that they are somewhere close to what they should be.
Bear in mind I'm only talking about a 5-20 mph up and down ride here up and down the back road by my garage, nothing fast yet. But the steering really snatches in like a kids scooter wheel.
Sideshow#36
26-02-08, 02:19 PM
I used to have the riser dogbones on my road SV and while the size difference was minimal it does make the bike steer a little quicker. Not too sure about the GSXR shock though? Do the wirral guys have the same Minitwins regs as BEMSEE? Because I had to replace the dogbones back to the originals as part of the regs.
I used to have the riser dogbones on my road SV and while the size difference was minimal it does make the bike steer a little quicker. Not too sure about the GSXR shock though? Do the wirral guys have the same Minitwins regs as BEMSEE? Because I had to replace the dogbones back to the originals as part of the regs.
Do you know what size the original dogbones are?
Sideshow#36
26-02-08, 02:49 PM
Sorry mate I cant remember the exact sizes. All I can remember is that if the dogbones are shorter it raises the rear making the bike turn in a little quicker. Not much help seeing as you dont have anything to go by. I'll try and measure mine as accurately as possible this evening and let you know.
Ok thanks. The ones on the bike have '17G' stamped on the side of them, not sure what that means. anybody?
Bear in mind I'm only talking about a 5-20 mph up and down ride here up and down the back road by my garage, nothing fast yet. But the steering really snatches in like a kids scooter wheel.
That would make sense with the longer dogbones. Steeper steering angle, less rake and trail. Have you tried backing the rear preload off all the way to see if that has any effect? If it calms things down it would confirm that the dogbones are the problem.
Carl
Blue_SV650S
26-02-08, 08:35 PM
That is the 70 profile front have on the front making it do that ... (being a race bike I presume you have a 70 section front tyre?!!? ;))
The 70 profile at slow speed if friggin horrid ;)
So if you have a 70 section tyre, don't fret, perfectly normal behaviour at <20 mph!! 8)
If you have a 60 section - we have a problem ;)
sv650k4
26-02-08, 08:56 PM
Two things I thought of, the rear dog bones may be none standard length. The ones on it are approx 150mm between centers.
i have a set of dog bones sitting in my garage that came of a normal faired bike not the nacked bike and the total lengh from 1 end 2 the other is 180mm so it seems yours are a we bit shorter.
;)
sv650k4
26-02-08, 08:58 PM
it could be the gixer shock 2 as ive herd people say they dont really suit the sv all that well tho im not a 100% sure on it as ive never tryed one before!
northwind
26-02-08, 09:15 PM
Do you know what GSXR shock it is? If it's a recent one it shouldn't impact the ride height too much I think, if it's an SRAD one then it would though.
Ok, had a bit more time to look at this. I think the dogbones on it are the original standard length. The 'stock' length ones shown on this page are approx the same length as I have on it http://forum.svrider.com/showthread.php?t=64162 and the 17G code stamped on the side also features in the K3 workshop manual in a photo of them.
So, I spoke to Rob from PDQ (also posts in this forum from time to time) and he told me to forget about using the K4 1000 shock for racing as its totally inadequate. With this in mind I've got a loan K3 standard shock coming (thanks Richie) to get me by and I've ordered an Ohlins race shock that I'm told will take three weeks :-(
The front forks are set as they should be with the top of the stanchions flush with the top of the top yoke (yoke from a naked which is a little thicker than the S).
I measured the sags for static and rider and although they werent perfect they certainly werent anything way out.
I've had the shock and linkages out of the bike tonight to inspect them and I cant see anything drastic, no binding anywhere and everything moved freely. Only minor thing was a very small amount of play in one side of the swingarm bearing. Thats a job for sometime this year.
Blue, the tyre on it at the moment is a 120/60 Metzeler I think so not as tall as a race tyre. It will have Pirellis on it pretty soon so that might in fact help by raising the front ever so slightly. Am I right in thinking that?
So the only thing I can really put this down to is the rear shock. I wonder just how different in length it is to a standard shock. It measures 333mm approx between centers of the mouting holes. If any of you have a stock K3 shock please drop a tape measure along it and see how it compares.
I'm totally open to any ideas on this and would appreciate any help you can offer. Thanks so far for the comments.
Do you know what GSXR shock it is? If it's a recent one it shouldn't impact the ride height too much I think, if it's an SRAD one then it would though.
It has K4 1000 written in yellow marker, I guess the breakers did that. I did a quick ebay search too and it seems to look the same as other K4 GSXR shocks. It measures approx 333mm between centers.
northwind
26-02-08, 11:15 PM
OK, I don't think the shock length is the issue here then, according to Kuhnco's figures the K4 1000 shock is 332.5mm eye to eye, and 480lb/in. The standard pointy SV shock is 330mm and 430lb/in. I have no idea what's actually causing hte problems you describe, but if the dogbones are standard and the shock really is a K4 item, it's not that. TBH if that's the case, then the Ohlins isn't going to make any difference to your problems (though it's going to be a nice piece of kit, I love mine) I don't have any race perspective on this, RobW is a top bloke though, but I reckon you could find some different opinions on the shocks (and you'll find plenty of people on a minitwins grid without a proper aftermarket one I'm sure)
Put it this way, my bike is up high at the rear- an Ohlins shock at full length, and it used to have JHS dogbones in- and low at the front due to the GSXR forks, even with the 120/70 tyre it's still shorter. The SV's stock geometry is very conservative, adding height to the rear is usual pure benefit (though it overtaxes the stock shock). Mine has none of the problems you describe. I don't know what's causing it though.
chunkytfg
26-02-08, 11:21 PM
It has K4 1000 written in yellow marker, I guess the breakers did that. I did a quick ebay search too and it seems to look the same as other K4 GSXR shocks. It measures approx 333mm between centers.
Could it be thats there is actually nothing wrong with it and it just feels odd because of it being a new bike?
Could it be thats there is actually nothing wrong with it and it just feels odd because of it being a new bike?
Well thats possible I guess, but it does feel pretty severe to me. I need to fill and bleed the front brakes :-) which will allow me to test at a bit more speed in the local B&Q carpark.
Is the front tyre soft? that would do it.
Pod
chunkytfg
27-02-08, 12:18 AM
Is the front tyre soft? that would do it.
Pod
Thats the other thing...I take it you have race pressures in the tyre?
30psi in a cold tyre will feel like that.
My suggestion is to up the pressure to normal road pressures and if the problem persists then it's not that and carry on looking but if it does go away you know that when the tyres are hot from a cold pressure of 30psi you will have 34-35psi and all will be well
Thats the other thing...I take it you have race pressures in the tyre?
30psi in a cold tyre will feel like that.
My suggestion is to up the pressure to normal road pressures and if the problem persists then it's not that and carry on looking but if it does go away you know that when the tyres are hot from a cold pressure of 30psi you will have 34-35psi and all will be well
Ok thanks, I must admit I hadnt got to the finer points like pressures yet as I was intending on replacing the tyres pretty soon. I'll check the pressures, get my front brakes sorted properly and give it a bit more of a test.
Watch this space.
Blue_SV650S
27-02-08, 09:25 AM
To be fair, not only is the GIXER shock not much longer than the stock shock, but why the hell are you putting a stock SV shock in?
For racing purposes you want the rear lifted as high as possible, this will not only make it steer sharper, but give you that o-so-valuable and needed ground clearance ;)
Bearing in mind you can't use dogbones, I'd hate to race an SV with stock shock, you would be grounding out at every turn!! ;)
It's a seriously bad move putting a stock shock in it ... I have a curvy, so have used a ZX6 shock, not a GIXER one, but it's the same idea and it is notably better than the stock SV shock ...
As other have said, tyre pressures (although this tends to make the front sluggish) and new bike syndrome ... also have you checked the forks and yokes for straightness???
To be fair, not only is the GIXER shock not much longer than the stock shock, but why the hell are you putting a stock SV shock in?
For racing purposes you want the rear lifted as high as possible, this will not only make it steer sharper, but give you that o-so-valuable and needed ground clearance ;)
Bearing in mind you can't use dogbones, I'd hate to race an SV with stock shock, you would be grounding out at every turn!! ;)
It's a seriously bad move putting a stock shock in it ... I have a curvy, so have used a ZX6 shock, not a GIXER one, but it's the same idea and it is notably better than the stock SV shock ...
As other have said, tyre pressures (although this tends to make the front sluggish) and new bike syndrome ... also have you checked the forks and yokes for straightness???
Blue, the only reason I'm going to try a stock shock for size is to compare against the K4 1000 shock to elliminate that as an issue. More to settle my mind really. The forks and yokes seem fine but I'm going to strip the font and take another look.
I've looked the frame over visually too and I cant see any evidence of damage or creasing.
I think I'll also take a side on photo of the bike to post here to see if it looks strange.
Blue_SV650S
27-02-08, 10:10 AM
Blue, the only reason I'm going to try a stock shock for size is to compare against the K4 1000 shock to elliminate that as an issue. More to settle my mind really. The forks and yokes seem fine but I'm going to strip the font and take another look.
I've looked the frame over visually too and I cant see any evidence of damage or creasing.
I think I'll also take a side on photo of the bike to post here to see if it looks strange.
03-04 SV650 330mm 430# <<<==== stock 2nd gen...05 should be the same
03-04 GSXR1000 332.5mm 480#
Dude, it is 2.5mm longer ... if you are lucky that is going to equate to ~6mm at the saddle i.e. f-all ... and at 15mph in a carpark, its not like it is doing much dynamically ... the shock isn't your problem ;)
03-04 SV650 330mm 430# <<<==== stock 2nd gen...05 should be the same
03-04 GSXR1000 332.5mm 480#
Dude, it is 2.5mm longer ... that if you are lucky that is going to equate to ~6mm at the saddle i.e. f-all ... and at 15mph in a carpark, its not like it is doing much dynamically ... the shock isn't your problem ;)
I think you are right, I'm not disagreeing. Its a puzzler this one. I need a more extensive test ride to get a firm opinion so I'll give this a better try at the weekend. Cant really do much until my front brakes are sorted so will get that finished tonight. Just needs filling and bleeding.
Not really that comfortable about raggin along to test my suspension with no brakes :-)
ok, I think my heart rate is coming back to normal. I have a beer in my hand and I'm a little happier.
Stripped and refitted the swing arm, a couple of the bearings were a touch sticky so re-greased everything. Nice and smooth now. Stripped, regreased and rebuilt the headstock. Think the steering stem nut may have been a little loose, but not much.
Checked the tyres earlier today, set them to road pressures for now, front was a little low but then its a while since they've been checked so now worries there. Come to test ride it again tonight and .....holy crap, I could barely turn a corner without fear of falling off the damn thing again. Got it back into the garage and started to examine the wheels further. After some 10 mins of real close up examination it seems I have a faulty front tyre valve. Front tyre pressure dropped from 36psi to 20 in the space of three hours!
Jacked it back up to 36 psi and took it out before it had a chance to leak.....bingo. back in business.
Sounds stupid but the tyre felt real firm and not at all squashy. but the pressure gauge doesnt lie. :-) What a pain in the ass that was.
To satisfy my curiosity I let the pressure down to 30, felt a little dodgy, then 25 , not much change, then 20......woah! that last 5psi seems to be the point where the handling totally collapses.
Blue_SV650S
28-02-08, 09:41 AM
...
To satisfy my curiosity I let the pressure down to 30, felt a little dodgy, then 25 , not much change, then 20......woah! that last 5psi seems to be the point where the handling totally collapses.
Its prolly the sort of pressure where the tyre wall starts to fold/deform proper as it isn't supported by the air?!!?
At least you have it sorted now 8)
Its prolly the sort of pressure where the tyre wall starts to fold/deform proper as it isn't supported by the air?!!?
At least you have it sorted now 8)
Yeah, this is a big relief. Thanks everybody for all the ideas and help, sometimes you get so buried in a problem that you need a fresh mind on it.
I ordered the Ohlins shock anyway, not as a method of sorting this problem but just because RobW's advice was that I'm really wasting my time with the GIXER shock on the track. I was going to get one later in the year so what the hell, its on the way now.
On the upside, when doing the brakes last night I think thats the quickest and easiest brake bleed I've ever done, from bone dry it only took 20mins or so to get it nice and firm ....ooo errrr.
Blue_SV650S
28-02-08, 10:16 AM
I think it depends on how competitive you want to be ? if you want to be at the sharp end you need a race shock. It also depends on experience, as a rookie its less important ? as you are NOT a rookie, and presumably your FZR had a race shock? I think you?d get frustrated with not having a race shock.
If you are going to get one, indeed it makes sense to get one now!! ;)
The rationale I used to use just before a big spend was this ..
?Will it potentially save me from an off?? .. offs are expensive and can be painful. You soon get your money back if you avoid an off ..
Secondly, I am going to spend ~?750 on this weekend .. why scrimp and effectively waste that as I have not got this bit ..
Always worked for stuff that was <?500!! :D Unfortunately full race systems (~?1000 for a 4cylinder bike) and race rads were >?500 (they are about ?1300) and therefore hard to convince myself I needed ? and so expensive it mean that if I had them then I couldn?t afford to do the actual racing anyway, so what was the point!?! ;)
Unfortunately that has always meant I have never had a truly competitive bike and that has always eaten me up inside ? :cry:
I think it depends on how competitive you want to be ? if you want to be at the sharp end you need a race shock. It also depends on experience, as a rookie its less important ? as you are NOT a rookie, and presumably your FZR had a race shock? I think you?d get frustrated with not having a race shock.
If you are going to get one, indeed it makes sense to get one now!! ;)
The rationale I used to use just before a big spend was this ..
?Will it potentially save me from an off?? .. offs are expensive and can be painful. You soon get your money back if you avoid an off ..
Secondly, I am going to spend ~?750 on this weekend .. why scrimp and effectively waste that as I have not got this bit ..
Always worked for stuff that was <?500!! :D Unfortunately full race systems (~?1000 for a 4cylinder bike) and race rads were >?500 (they are about ?1300) and therefore hard to convince myself I needed ? and so expensive it mean that if I had them then I couldn?t afford to do the actual racing anyway, so what was the point!?! ;)
Unfortunately that has always meant I have never had a truly competitive bike and that has always eaten me up inside ? :cry:
yeah its a tough call. I did use a Maxton race rear on the FZR and it was seriously light years better than the stock one it replaced.
The good thing that attracted me to the mini-twins class though is that some of the silly money can be avoided such as serious engine upgrades. Yeah I've spent alot prepping this bike but its all up front cost that I shouldnt have to respend for at least a few years worth of racing. I'm not sure there is anything left for me to upgrade within the rules so off to a good start so far. The only thing I havent bothered with up to now is a steering damper. Now that I'm happier with the bike again I can live with that.
In the formula 400 class there were lads spending ?1800 on a balanced and lightened crank shaft! for gods sake! I just wasnt prepared to spend that kind of money.
Fingers crossed then it should be a good season. I was fighting for top three positions on the FZR with a seriously underpowered engine compared to the other guys, had a couple of wins on it too. Pretty annoying though when you fight your way to the front then some guy passes you on the straight with 20mph advantage.
Blue_SV650S
28-02-08, 10:49 AM
...
I 'hear that' :rolleyes:
What annoys me about the minitwin regs is that it only lets people get expensive power ... like you can't do the wire chop TRE mod and/or chop up your OE filter to improve flow and/or install a inlet cam on your exhast but you can (and therefore need to if you want to be at the sharp end!) get a full titanium race system and a BMC race filter and buy full set of pointy cams ... including DYNO time and labor ?1500-?2000?? I could have got similar results from the former for a tenth of that! ;) :rant:
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