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Preload on a gsf250

Discussion in 'Technical and Troubleshooting Torque' started by fingers89, Apr 2, 2008.

  1. Hi everyone, i was just wondering if anyone knows if i can adjust the preload on my 250 bandit? I want to make mybike taller in the rear, so i can lean harder. I find i could lean more but my pegs scrape the ground too much, and it prevents me from getting it over anymore.

    will the change give me any adverse effects in handling, cause it ahnaldes awesome as it is.

    thanks for all the help in advance guys.

    p.s, is it easy to do? im quite mechanically minded, but im not sure what im doin with suspension set ups.

  2. I don't think increasing rear suspension preload will increase your ground clearance. It will just make your suspension stiffer and raise your seat height by allowing less sag :-k
    PS: If you are scraping the pegs, isn't that an indication that you are reaching the lean-over limit of the bike ???
  3. I have to say im 100% with VCM on this one...

    making the rear suspension (or preload) will only give your bike a harder ride...

    scrapping the pegs is a CLEAR sign that your getting close the bikes/tyres leaning limit...

    just a warning do not lean further once the pegs are scrapping. i had a bad experince with that... :(
  4. Remove the pegs?! haha
  5. Or that the springs/shocks are stuffed, or that your riding style is wrong.
  6. No, the pegs on the GSF250 are really low. I hang a fair way off and I've still got a fair few scrapes on my boots.
  7. Yeah second class citizen is right, the bandits have really bad ground clearence, the tyres seem to have plenty of room left, at least 2mm-3mm casue thats the size of my chicken strips, it hangs on well through corners, and absorbs bumps well enough.

    I really just need ground clearence. Is there anyway to achieve this?

  8. Of course it will change the ride height, unless it is already cranked right up. More ride height = more ground clearance.

    Just do it to your own bike to see what happens.

    Since the bulk of the rider's weight is normally over the rear wheel, and acceleration adds to that loading, it is usually more effective to add rear preload, especially if you also carry eiother a passenger or lots of books to uni.

    Even if you don't, adding preload lifts the back end. Just measure before you do it to see what happens.

    Actually, it does not make your suspension "stiffer". If you had 20kg/cm springs before you made the adjustment, they will still compress at exactly the same rate. In other words, it will still take 20 kg to compress each spring one cm - with dual shocks that means a total weight of 40kg needs to be applied to compress the back end of the bike 1 cm.

    It does mean that you will have an extra 80 kg of load capacity of you do add 1cm of preload adjustment, but that is it.

    It raises the seat height as well as raising the peg height. Since the pegs are closer to the forks (the effective pivot point when you raise the back end) they won't rise as much as the back of the seat.


    Trevor G
  9. It doesn't make the ride "harder" either. It raises the back end unless the preload is adjusted so much that the bike does not sag at all under the rider's weight.

    Just because the bike does not sink as much under the rider's weight does not mean it is stiffer - it is just riding higher for the same weight. This reduces the fork/steering angle which helps to make the bike turn in more quickly. That is often a good thing.


    Trevor G
  10. Does it have twin shocks? Then you have cam adjusters on the bottom of each shock.

    If it's a monoshock there is usually a threaded adjuster at the top of the shock. Usually. And not always easily accessible, either.

    Measure the clearance between your tyre and the underside of the guard, or the distance from the top of the swingarm to the top frame tube just above, when the bike is off the stand and vertical.

    Then sit on the bike and measure again.

    Adjust the preload and recheck the measurements.


    Trevor G

    PS Also check that the tyres fitted are the correct size for the bike. Some sizes allow for a low profile tyre to be fitted when a higher one is better. The profile is the second number in the tyre size, and represents the percentage that the sidewall is "less" than the tread or carcase width.

    A 110/90 rear has a higher profile than a 110/80, by about 11 mm. That could make quite a difference as well.
  11. It does? Might have to have a bit of a muck about with it tomorrow.
  12. Thanks for all your help trevor g. the tyre on the rear is a 140/70, and it is the right size tyre for the bike. as far as the shocks go, it is a monoshock spring,a nd you are alos right about being inaccesable. it looks like a biatch to get to, but ill have a crack on the weekend. Ill get my mate to give me a hand for all the measurements,a nd an extra pair of hands shouldnt hurt.

    P.s. can anyone tell me any odd tolls i might need. i already have 1/2, 3/8 and 1/4 inch high quality socket sets. 20 different screwdrivers (both size, width and type, pliers (of all kinds), plenty of high quality spanner sets.

    Thanks for all the help guys, and anymore will be appreciated.

  13. Yours has a 140/70 rear? That can't be right. Mine has a 150/60 rear, which is what the swingarm label and the manual list as the correct size.
  14. Yeah im pretty sure the aussie import is different. mines a grey import, and it has plenty of different features, despite being labbelled as the same bike. (makes finding parts really fun :roll: ). But that is the standard tyre for mine. i kinda wish i had a thicker tyre though, and ill admit i have thought about putting one on.

    cheers fingers89
  15. Increasing preload is a bodgy way of getting slightly more ground clearance. It is better to space the suspension. I'm not sure what the arrangement is on the GSF, but on my YZF750 the top shock mount is a threaded bar that sticks vertically out of the top of the shock, though a hole in the frame, and a nut secures from the top.

    I added a collar- effectively just a 15mm piece of thick tube- so the frame sits higher relative to the shock. This allowed more ground clearance, and I could drop the front a little to get better turn-in speed (quicker steering).

    If you shock has an eye at both ends you would need to machine a part. Another option is to change the 'dog bones'- the steering linkages on the bottom of the shock that attach to the swingarm, usually via a casting that creates/controls the rising rate of the suspension.

    Having thus shown you the guns, I would strongly recommend you either don't modify the suspension unless you know EXACTLY what you're doing- because it's hard to get just the change you want without getting potentially dangerous changes you DON'T want. For instance I was happy to get the xtra steering speed because the YZF is dead stable... but if your bike turns in fast it will just become dangerous and unstable.

    You should hang off the bike more and it will be less inclined to touch down. Also, riding at maximum lean is not the same as riding fast... it just means you spend more time on the limit of your tyre adhesion and your luck, and you can't get the power down if you are at max lean.
  16. Yeah 140/70 sounds right, my grey import Kat runs the same (essentially the same frame/engine as the Bandit). You may find the grey-import Bandit has much shorter and/or softer springs - that seems to be the case for most JDM bikes designed more for lower speeds and for potholed city streets.
    I'd definitely recommend checking (or getting someone to check) the suspension on the bike - mine had no oil whatsoever in the front forks when I got it (which somehow escaped the notice of a RWC, at least one "professional" service and two previous owners :roll:). Fixing that certainly helped with cornering ;), and I never had a problem with the pegs touching the ground even though I certainly used all of the rear tyre on more than a few occasions. Of course the Kat did have the advantage of having both preload and rebound adjustment on the rear, I found setting both fairly close to maximum gave the best handling (for me), though stiffer front springs and a bit more adjustment (other than changing fork oil viscosity) would have been nice.