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Mechanical and Technical Mechanical and technical topics, help, and discussions

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Jul 2nd 2016, 04:53 AM   #1
 Squidly's Avatar
 
  Jan 2016
  Bothell

Geometry/Suspension help

Any suspension gurus here? What suspension or geometry changes should I make to get a bit more front end traction and a bit less in the rear?

It's a low HP bike and in the dry I've only been ever to kick out the rear once, however I'll tuck or push the front end all the time in every stage of the corner.

Bike is an SV650 with gsxr front end and gsxr rear shock+raising dogbone. The front sits 10ish mm lower than stock and the rear is higher. I have a halfway decent baseline right now, but no expert has ever fooled around with the geometry.

My theory is I want more rake and possibly to stiffen up the rear compression and rebound. Is this right?

Any input would be greatly appreciated because I don't really know what I'm doing lol.

Also, would taking weight off the front help or hurt? I could probably lose 10lbs over the front end if I streetfightered it...
Jul 2nd 2016, 11:06 PM   #2
 PeteN95's Avatar
Moderator
 
  Jan 2016
  Muklilteo, WA

  Suzuki DL1000, Honda XR650R, KTM 250 XC-W
Your tucking the front when, steady cornering (light throttle) or accelerating out of the turn (heavy throttle)? If its the latter, you need more weight on the front because your unweighting it with acceleration. If its the former, sliding the forks down 10mm in the triple clamps (more rake) might help.
Jul 2nd 2016, 11:37 PM   #3
 Squidly's Avatar
 
  Jan 2016
  Bothell

I've actually had both, I've tucked the front under steady throttle and I've gotten some serious push under WOT. My bike isn't lifting the front that much at 80 though so I'll try dropping the forks.

Thanks dude!
Jul 5th 2016, 09:43 AM   #4
 jared p's Avatar
 
  Jan 2016
  here

  there
go see Optimum Performance Motorsports in Totem Lake just south of you and have them set it up professionally for $40
Jul 5th 2016, 10:24 AM   #5
 mgfchapin's Avatar
 
  Jan 2016
  Kirkland, WA

  '15 675R
2nd gen SV? What year GSXR forks? Does the GSXR shock and dogbone raise it back to stock height?
Jul 5th 2016, 11:12 AM   #6
 Squidly's Avatar
 
  Jan 2016
  Bothell

Thanks for the offer Jared. I'm sure you guys would nail it but I am a broke student and make it a point to do most of my own work.


Bike is 2nd gen. 04-05 750 front with (I think) an 08 1000 shock. With the dogbone the rear sits higher than stock but I'm not sure how much.
Jul 5th 2016, 11:25 AM   #7
 mgfchapin's Avatar
 
  Jan 2016
  Kirkland, WA

  '15 675R
I have the same front end as you but a Penske shock and (I think) stock dogbones. I like my bike pretty high in the back but the front is solid. The forks are 18mm above the triple, including top cap. The shock is 337mm long from the center of the top mount bolt to the center of the bottom bolt.

You're on the right track in that you probably need more rake. You should also take sag measurements to make sure your front preload isn't cranked down all the way.

A stock GSXR shock won't have much range of valving adjustment, but you can give it a shot. Where is comp & rebound now?

What tire brand, model & size are you running?
Jul 9th 2016, 12:03 AM   #8
 Squidly's Avatar
 
  Jan 2016
  Bothell

I just had a pair of Metzeler m7rrs mounted which I haven't had the chance to push much yet. 120/70 front and 160/55 rear. Previously I was running a hard old pair of dunlop kr106/108 with a 120/80 front and a 170/55, and before that I was on Q3s with a 120/70 front and 160/55 rear. I had a lot more drama on the Q3s but I was still getting some occasional front end push with the slicks.

The gsxr shock sits at 12 clicks out of compression and 13 for rebound. Forks are 2 half turns out for both rebound and compression. Preload on the forks is at the 3rd line and the springs are for a rider 20lbs heavier than me.

I know a nice shock would let me get a way better setup, but TBH I'm still learning how to tune suspension and wouldn't know what to do with the extra range of something aftermarket.

Edited by Squidly on Jul 9th 2016 at 12:05 AM
Jul 9th 2016, 09:06 AM   #9
 mgfchapin's Avatar
 
  Jan 2016
  Kirkland, WA

  '15 675R
Quote:
Originally Posted by Squidly
I know a nice shock would let me get a way better setup, but TBH I'm still learning how to tune suspension and wouldn't know what to do with the extra range of something aftermarket.
It's not just the extra range, it's that the damping adjusters actually do something throughout the whole range and it doesn't take 5 clicks to notice a difference.

Sorry I didn't ask before, but is this on track or street? What's your pace?
Jul 9th 2016, 01:14 PM   #10
 Squidly's Avatar
 
  Jan 2016
  Bothell

I ride track and street, but I set my suspension for the track. I was running just over 2:00 at the Ridge when I was on the dunlop slicks. Upper B group.

Did you notice the penske making a difference in your lap times?
Jul 9th 2016, 02:01 PM   #11
 mgfchapin's Avatar
 
  Jan 2016
  Kirkland, WA

  '15 675R
I've never ridden an SV with a GSXR shock, but the thing that comes stock isn't even worthy of the term "shock." The Penske gives me as much confidence as the TTX on my 675R.

I think I know what's going on. Try dropping your forks maybe 5mm and see if that helps. Go in on the shock at least 3 clicks on comp and rebound. Most of all though, lean more. Above 2 min at the Ridge, I have the same symptoms as you. Flighty front end that feels like it wants to wash out. If I go a little faster and give it more lean, I get off the transitional profile of the tire and onto the shoulder where it feels planted. The Dunlops are especially steep so I can see how that sensation would be intensified.
Jul 9th 2016, 03:02 PM   #12
 Squidly's Avatar
 
  Jan 2016
  Bothell

Thanks for the help! I'll try dropping the forks a bit but I don't think I need to lean more. I was only feeling the front push with the k106 when I had my elbow down or was close. I carry a good amount of corner speed in some parts of the track but I'm pretty slow in others so my times suffer
Jul 9th 2016, 06:24 PM   #13
 Wrench's Avatar
 
  Jan 2016
  West Richland, WA

I gotta say, this thread is so full of AWESOME.

I'm having similar issues with my mini moto, and this thread is helping a lot. Thanks, guys!
Squidly and SmokeyMcNug like this.
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