Ernie Panks Posted October 12, 2000 Share Posted October 12, 2000 We managed to get really baffled at the Norfolk meet last week on the subject of pre load adjustment on a diff and the effect it had on understeer to the extent that we waded out of the Cornwallis at closing time knee deep in bull**** and confusion! The only preload that I really understood was present in a diff was the pre load on the taper roller bearings that is normally adjusted at the input flange of the diff. Surely adjusting the bearings to a load either side of the optimum is going to take it's toll on bearing and gear life. Is there any further adjustment to be had from an LSD?? Has anyone got a real definitive answer as to whether or not this adjustment would yield results or is it a case of some mercenary sod trying to earn an extra few quid promising a spectacular result?!! R822CVG Link to comment Share on other sites More sharing options...
Peter Carmichael Posted October 12, 2000 Share Posted October 12, 2000 Plate type (Ford) limited slip diffs can be pre-loaded to give different amounts of lock up. The AP Suretrak is torque sensing and is non-adjustable; it self adjusts. Both types have been fitted to Sevens. The Suretrak has been standard fitment on roadgoing Superlights. The recent race cars have had plate type LSDs. Link to comment Share on other sites More sharing options...
Ernie Panks Posted October 13, 2000 Author Share Posted October 13, 2000 Thanks Peter, That's cleared that one up! R822CVG Link to comment Share on other sites More sharing options...
Jules Martin Posted October 13, 2000 Share Posted October 13, 2000 Ernie, speak to Richard Ince, he has been playing around with the pre-load settings on his R500 diff. Jules Link to comment Share on other sites More sharing options...
Shaun Soanes Posted October 13, 2000 Share Posted October 13, 2000 Jules, I'm sure Ernie would have come up with the same reply (Probably locked away in his garage building his superlight), but it was Richard that started this great debate. It seemed to be more specific to his R500, but I still don't understand why this affects under steer. Is that car on the road yet Erniequestion.gif Also the harness buckle change over description I sent you needs modifying. Call me if you can't solve it or need further info. tel: 01206 306034 Shaun Link to comment Share on other sites More sharing options...
Peter Carmichael Posted October 13, 2000 Share Posted October 13, 2000 Well it sounds like the R500s are on a plate type diff then. This makes sense, because if you go kerb hopping on the circuit with a torque sensing diff, when you get an inside wheel in the air off a kerb, the diff will essentially go open and the inside wheel will spin up dramatically. If you have 200bhp or more and big slicks/ACB10s this will cause a problem when you land because the spinning wheel will be decelerated rapidly and you will get a shock load heading all the way back up the drivetrain. Recent six-speed gearboxes have an improved 5th gear to prevent it shedding its teeth (mine has been upgraded and I have reviewed the two gears), but this mode of usage will cause problems elsewhere at the weakest link. With a plate type diff, this doesn't happen. The locking action is pre-set and will still be acting when the wheels are in the air. When you have too much lock up in the diff, the inside wheel will try to turn at the same speed as the outside wheel in a corner, straightening the car up and causing understeer. Adjusting a plate-type diff is a matter of setting the minimum pre-load which avoids rampant wheelspin from the inside wheel. Link to comment Share on other sites More sharing options...
Shaun Soanes Posted October 14, 2000 Share Posted October 14, 2000 Thanks Peter, it begins to make sense now, i'm sure it will be discussed further at our Norfolk meet. Shaun Soanes Edited by - shaun soanes on 15 Oct 2000 00:12:41 Link to comment Share on other sites More sharing options...
Richard Ince Posted October 15, 2000 Share Posted October 15, 2000 The pre-load on the diff that Caterham supplied for my R500 was 58lbs. Driving with that much pre-load made the car understeer badly. The pre-load has now been reduced to 38lbs and the understeer has now disappeared. The lap times have improved. The R500 has a ZF diff compared to the AP that the Superlight R runs. The main difference is that the ZF can cope with one wheel in the air and the AP struggles. Link to comment Share on other sites More sharing options...
Chelspeed Posted October 19, 2000 Share Posted October 19, 2000 Thanks for the pre-load explanation Peter, that's the first time I've understood why it causes understeer, obvious really... What about ramp angles? When SPC 4.44'd my diff he also recomended chnaging the ramp angles from Caterham's shopping setting to something more appropriate. From 30deg to 45deg or vice verse, something to do with the speed of it locking up. Can you give an equally simple explanation of the effect of this change and the interaction with pre-load, if any. Link to comment Share on other sites More sharing options...
Ernie Panks Posted October 19, 2000 Author Share Posted October 19, 2000 ARRRRRRGGGGHHHHH!!!! Ramp angles??? Oh no next month's meeting is going to be devoted to an in depth discussion on ramp angles! I'm going to have a lie down in a dark room now! R822CVG Link to comment Share on other sites More sharing options...
Shaun Soanes Posted October 20, 2000 Share Posted October 20, 2000 Ernie you haven't got time to worry about ramp angles. Hows the build goingquestion.gif Link to comment Share on other sites More sharing options...
Ernie Panks Posted October 23, 2000 Author Share Posted October 23, 2000 Build was going ok until I got a dodgy diff. The driveshaft just refused to go in whatever I did (apart from walloping it!) Picked up new diff and drivshafts from Caterham on Saturday. Only had yesterday pm on the car, I have managed to finish most of the rear suspension now. I am hoping to be completely finished by the weekend, then it's post build check, SVA and Wahhaaaayyy!!! I'm on the road! Link to comment Share on other sites More sharing options...
Ernie Panks Posted October 23, 2000 Author Share Posted October 23, 2000 By the way, I didn't wallop it, it just reads that way! Link to comment Share on other sites More sharing options...
EFA Posted October 24, 2000 Share Posted October 24, 2000 I spend a day or so talking with Phil Stewart of Road Race Transmissions on these precise subjects. The Preload is an adjustment on a ZF diff (identified by two shafts crossing the centre of the diff when you peer down the driveshaft holes). Stock they are set upi at 58lbs which is appropiate to a car weighing 1500kgs. For a Seven RRT's tests have revealed about 36 -40lbs to be ideal. This reduces understeer or rather it places it earlier in the corner, thus enabling you to get on the gas quicker. The ramp angles effect straight line acceleration only. With 45deg ramps (std) the diff locks more suddenly and is therfore not as responsive to minute throttle adjustments in controlling wheelspin and the drive is more susceptable to small bumps under and individual driven wheel. Me?? I'm changing both, and the drive ratio as my 168mph (top gear is rather silly. Anybody want a 3.38:1 ZF LSD??? AW Link to comment Share on other sites More sharing options...
J.R. Posted November 8, 2000 Share Posted November 8, 2000 Arnie I am looking for a 3.38 L.S.D. If yours is for sale E-Mail me with price, I have bought some bits from you before & am local Link to comment Share on other sites More sharing options...
Slipper man Posted November 9, 2000 Share Posted November 9, 2000 Does anyone know how you adjust the pre-load? Is it something I can do myself, before I fit the diff to the car? I assume ramp angles are fixed, and require new parts. Link to comment Share on other sites More sharing options...
John Richens Posted November 9, 2000 Share Posted November 9, 2000 Keith, place one of your tartan slippers over each side of the diff and hit them with a hammer ! Link to comment Share on other sites More sharing options...
John Richens Posted November 9, 2000 Share Posted November 9, 2000 I apologise ,I forgot that this is the Tecci area blush.gif Link to comment Share on other sites More sharing options...
Slipper man Posted November 9, 2000 Share Posted November 9, 2000 Do some work! (they aren't tartet anyway - they are high quality suede) Link to comment Share on other sites More sharing options...
Slipper man Posted November 9, 2000 Share Posted November 9, 2000 They aren't tartan either blush.gif Link to comment Share on other sites More sharing options...
Peter Carmichael Posted November 9, 2000 Share Posted November 9, 2000 Its easy to fix if you take it to Phil Stewart... Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now