To LSD or NOT that is the question

[DTRguy]

On our ITC Rabbit we have a welded diff... on our previous ITB Audi coupe we were open, and then went with a Quaife... Now, I have been told with such a LOW hp (basically <100hp) that it could be set up without a LSD or welded, suspension wise and the car would actually be much faster. This by maintaining more speed through the all important turns because of less tire scrub. In fact the information came to me from a well known chassis setup engineer/driver that took a podium in NASA Nationals with a 140hp neon with open diff. Thoughts?

[zchris]

I completely agree that open on low HP cars is almost always faster to run an open diff. Your corner entry and mid corner should have much less understeer. This will inturn keep your tires from overheating early on in the race. I run my FP Miata with a loose(turn it by hand) posi out of an RX7. Until I absolutely need it its an open diff. Poeple who say there car is much better with a welded diff just have not set there car up properly. Welded or high preload rob you of HP and overheat your tires. The fastest lap I ever turned in my old GT2 car at Limerock was duing the race after the posi unit preload spring broke. I got wheel spin at 120mph but the car never turned so well.
Chris Howard

[seckerich]

Like Chris said if you run a LS unit set it up with just enough preload to keep from spinning when you lift the inside tire.

[joeg]

open?... for rain...maybe.

There is no doubt a Limited Slip helps...any car.

I have a Quaife, I have a PG, I have a welded Diff. The only issue with the Quaiffe is that they are HEAVY;

The only issue with the PG is...not as good as the Quaife.

Welded Diffs work well but introduce all kinds of CV issues (paddock breakage) and have diabolical characteristics in wet conditions.

To have any modicum of track speed (whatever the HP), you have to address the diff.

[DTRguy]

Here it is in simple form. I'd like to get my new race car set up fairly quickly and as economical as possible. (81 scirocco ITC) So, we have a tranny. Initially based on how much I enjoyed driving the Rabbit ITC car with the welded diff, I thought we'll just tear the tranny apart and drop in our other welded diff... or I can weld that one up. In any case, that would mean more work, possibly more money, etc etc. Recently though I was told don't bother. Re adjust the suspension so that the front wheels stay more planted and run it open. More tire life, better turning, overall faster. I am used to HUGE hp FWD cars (I have built a few turbo VW's) and a Peloquin is standard equipment on those. And most of my other experience is with autocross. Both instances a torsen works very well. I have never considered not running one until now... faced with a tighter budget and the thought that it would be faster without. I am probably going to throw it together and run open at least for the interim. I wanted to hear feedback from others on their experiences... Keep it coming I wanna hear about it! Thanks!:D

[Lael Cleland]

I was doing laps at MAM with an open diff in an 84 GTI, 1.56. installed a peloquin, 1.56s, blew up the engine, new pistons, new every thing, TT race header, 1.56s, small front sway, no front sway, BIG front sway bar=1.56.....in a race with perfect conditions, and new V700s it did a 1.55 with an open diff? At a track day last week, different header, with junk tires 1.56...
I think you can set up a vw to not need an LSD, If there is no tire spin coming out of corners, it is not needed?.?...I Hate welded with wimpy rabbit hubs/bearings!

Its all opinion, there's a bunch of people that have been racing rabbits longer than I.......
Lael

[Knestis]

Ultimately, I think it comes down to driver style. We ran a welded diff in the MkIII Golf at the ARRC and I was reminded that I actually like how they work - back from the olden days when we had just two choices, welded or nada.

My FIRST choice would be a proper clutch-type diff, with enough test time to get it set up right. That means servicing the gearbox all the time, $$$, more $$$$, etc. That would be a good compromise for sprints and enduros with rental drivers.

For SPRINT races, I think I'll go with a spool - which I have "in stock." They are hairy in the wet but if you just let them run their course, they are not horrific - at least not on an FWD car. (But note that I like rain.) I frankly don't buy the "hard on parts" thing, unless one does dumb stuff in the paddock. The tires are - or should be - always sliding at least a little on the race track, which should be enough compliance that it's not doing significantly more harm to bits, than would racing under the best of circumstances.

For ENDUROS with changing conditions and drivers who might not be so comfy with surprises, we use the Peloquin but honestly, I don't think it's any quicker than an open diff.

...but different driver preferences and styles might well make any one option better than the others for typical use. I *like* the fact that the spool/welded diff reinforces being ON the gas in situations (a la mid-corner incipient understeer) would encourage LIFTING with an open diff. I also like being able to effectively use a couple feet of grass on the inside of a corner if I have to.

K

[DTRguy]

I was doing laps at MAM with an open diff in an 84 GTI, 1.56. installed a peloquin, 1.56s, blew up the engine, new pistons, new every thing, TT race header, 1.56s, small front sway, no front sway, BIG front sway bar=1.56.....in a race with perfect conditions, and new V700s it did a 1.55 with an open diff? At a track day last week, different header, with junk tires 1.56...
I think you can set up a vw to not need an LSD, If there is no tire spin coming out of corners, it is not needed?.?...I Hate welded with wimpy rabbit hubs/bearings!

Its all opinion, there's a bunch of people that have been racing rabbits longer than I.......
Lael


GREAT feedback! This is kind of what I would expect!


Ultimately, I think it comes down to driver style. We ran a welded diff in the MkIII Golf at the ARRC and I was reminded that I actually like how they work - back from the olden days when we had just two choices, welded or nada.

My FIRST choice would be a proper clutch-type diff, with enough test time to get it set up right. That means servicing the gearbox all the time, $$$, more $$$$, etc. That would be a good compromise for sprints and enduros with rental drivers.

For SPRINT races, I think I'll go with a spool - which I have "in stock." They are hairy in the wet but if you just let them run their course, they are not horrific - at least not on an FWD car. (But note that I like rain.) I frankly don't buy the "hard on parts" thing, unless one does dumb stuff in the paddock. The tires are - or should be - always sliding at least a little on the race track, which should be enough compliance that it's not doing significantly more harm to bits, than would racing under the best of circumstances.

For ENDUROS with changing conditions and drivers who might not be so comfy with surprises, we use the Peloquin but honestly, I don't think it's any quicker than an open diff.

...but different driver preferences and styles might well make any one option better than the others for typical use. I *like* the fact that the spool/welded diff reinforces being ON the gas in situations (a la mid-corner incipient understeer) would encourage LIFTING with an open diff. I also like being able to effectively use a couple feet of grass on the inside of a corner if I have to.

K

Also fantastic feedback... thank you very much... and well I completely understand some of the benefits of the welded/spool... I Personally experienced what happens when you trailbrake too long into a fast corner with a welded and what it takes to correct it (in the rabbit). And who wouldn't want a little extra room by using the grass right? :happy204: All of this feedback is honestly reinforcing my desire to focus on the suspension and not the gearbox. Ie spend the money where it counts.

[RSTPerformance]

In our Audi's we gained 2 seconds a lap a some tracks, while others we didn't notice much difference. I think it completely depends on the car and more importantly the track.

We have 20 years worth of development in the Audi suspension (10 years times 2 cars) yikes we are getting old... with that we are still not experts but we have learned a lot. We originally were going to buy a already tested product but found that not only was it out of our price range at the time but also knowone seemed to agree on the "best" set-up. We went to california and the best known west coast shop built a completely different set up than the best northeastern shop. Totaly different ideas on set-up from swaybars, spring rates, different struts, quaife/no-quaife, etc. In the end we did our own testing and built something different than both lol. One thing though is that we noticed that in the northeast tracks are short and tight while the west coast and in other areas of the contry not so much... did this play into the set-up designs? hummm... maybe everyone was right!

Raymond 'In the northeast, I am a believer in the Quaiffe" Blethen

PS: If you want to learn how to drive with a Quaife, take the racecar Ice Racing.... you will learn a lot!

[joeg]

Raymond--Take a welded diff on the ice; a Quaife is far too easy to learn.

[DTRguy]

In our Audi's we gained 2 seconds a lap a some tracks, while others we didn't notice much difference. I think it completely depends on the car and more importantly the track.

We have 20 years worth of development in the Audi suspension (10 years times 2 cars) yikes we are getting old... with that we are still not experts but we have learned a lot. We originally were going to buy a already tested product but found that not only was it out of our price range at the time but also knowone seemed to agree on the "best" set-up. We went to california and the best known west coast shop built a completely different set up than the best northeastern shop. Totaly different ideas on set-up from swaybars, spring rates, different struts, quaife/no-quaife, etc. In the end we did our own testing and built something different than both lol. One thing though is that we noticed that in the northeast tracks are short and tight while the west coast and in other areas of the contry not so much... did this play into the set-up designs? hummm... maybe everyone was right!

Raymond 'In the northeast, I am a believer in the Quaiffe" Blethen

PS: If you want to learn how to drive with a Quaife, take the racecar Ice Racing.... you will learn a lot!

The Blethen Brothers? You know we've met! I helped you guys at Mid O a couple years ago when you came down with a suspension upright. Elliott Bavely is my racing partner... We retired the coupe :( He runs the Rabbit now(with the welded diff) and I picked up the Scirocco.

I can see where a tighter track might have an advantage with a LSD. Maybe even at Mid O where we are mostly. However, I also wonder if the problems could driven around with a change of driving style and suspension setup. And in the end potentially go faster with less tire wear?

Thanks for your input!

[RSTPerformance]

At Mid Ohio I think you have a few key turns that will need something... Such as the last right hander into thunder alley (?). Did you ever sell the coupe?

Raymond

[DTRguy]

At Mid Ohio I think you have a few key turns that will need something... Such as the last right hander into thunder alley (?). Did you ever sell the coupe?

Raymond


yeah you may be right about that turn in particular... I think that based on my current financial position it was basically between dropping a welded or leaving open. Even the welded is going to cost something. The Coupe was/is Elliott's and no I believe it is still at his house under a cover. I don't know what his plans are with it at the moment.