cambered rear ends: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 13, 2008 7:04 p.m. kevlarcorolla New Reader

So I have an ae86 and have made some substancial improvements,with the new turbo'd 4ag I put together I have even more trouble with rear grip. In an effort to find a little more mid and corner exit rear grip I've been looking for info on adding camber to the live axle.The car is track only used for autox,time attack and track day fun.

Didn't find all that much in the way of tech info surprisingly,some discussion on turbobricks and that was about it.With the stock car stuff they use special drive plates etc etc to make them work.

I know the different ways to bend the tubes but does anyone have any real experience with bearing and axle life?.If I could use the stock parts and get about -1 camber I'd be happy.
Dec. 13, 2008 7:10 p.m. AngryCorvair Dork

44dwarf will be able to tell you with good firsthand experience, i'd bet.

how much of your roll stiffness is coming from your rear suspension? maybe you need more front roll stiffness, combined with more front camber and/or more front toe-out and/or more front tire.
Dec. 13, 2008 7:22 p.m. kevlarcorolla New Reader

I have no trouble with front grip,in fact I'm tuned to reduce front grip for neutral balance.If I can improve the rear a little more than I can dial some more front grip to rebalance the car. I have the car set-up fairly soft and no rear bar,front aftermarket bar usually set on the softest setting.

Here's a quick action shot.

http://i117.photobucket.com/albums/o50/kevlarcorolla/CopperCorollaProfessionalPic.jpg
Dec. 13, 2008 7:45 p.m. Trans_Maro New Reader

I've cambered a KP61 Starlet axle before.

Jig up the axle housing so it won't move around on you.

Cut most of the way through each tube from top to bottom but not all the way through. Make the cuts an equal distance from the center on each side. I cut mine where the banjo section began to straighten out. I used a sawzall, the cut was about 1/16" wide

Lift the end of the tube up enough to close up the saw cut at the top and tack weld it to hold in place. Do the same for the other side and check each tube with an angle finder to make sure you've got them both the same.

You can trial fit the third member and axles at this point to make sure you haven't gone too far and created a bind.

Weld the tubes back up again and re-assemble.

There's enough play in the side gears and splines that they can tolerate a bit of mis-alignment without creating excessive wear.

I autocrossed my Starlet this way for about three years without any rear end trouble. I can't reme,ber how much camber I gained though, probably about 1/2 - 1 degree at most.

I've heard of guys heating and bending the housing in a press as well.

Good luck

Shawn
Dec. 14, 2008 12:50 a.m. joey48442 Dork

kevlarcorolla wrote:

I have no trouble with front grip,in fact I'm tuned to reduce front grip for neutral balance.If I can improve the rear a little more than I can dial some more front grip to rebalance the car. I have the car set-up fairly soft and no rear bar,front aftermarket bar usually set on the softest setting.

Here's a quick action shot.

http://i117.photobucket.com/albums/o50/kevlarcorolla/CopperCorollaProfessionalPic.jpg

Hey!

You got paint on your headlights.

Joey
Dec. 14, 2008 8:27 a.m. blaze86vic New Reader

What you want to do is a full floater axle. Don't try and bend the housing or anything Jerry Rigged like that. Your AE86 is way too nice to do a hack job.

Talk to Spence Weir, of Weir Performance. He he can help you get the kit in the link to work with your car. It's already designed to bolt up to a 6.7" toyota rear end and you don't have to cut or weld anything on the car at all.

http://www.dwarfcarproducts.com/ 707-315-6638
Dec. 14, 2008 9:37 a.m. blaze86vic New Reader

I think he is already a little past that.
Dec. 14, 2008 11:30 a.m. Trans_Maro New Reader

blaze86vic wrote:

What you want to do is a full floater axle. Don't try and bend the housing or anything Jerry Rigged like that. Your AE86 is way too nice to do a hack job.

Either way works. Cutting or bending has been done for years and doesn't cost $1100 in parts alone.

If it didn't work, nobody would have done it.

I love how this is considered "Jerry rigged" but using rusty, scrap battery trays from E30's to trunk mount batteries is "Grassrooots" when you can buy a proper battery mount for less than $100.00

Some days you guys really amaze me.

Good luck with your Corolla, it looks badass :)

Shawn
Dec. 14, 2008 12:08 p.m. Varkwso Reader

Trans_Maro wrote:

blaze86vic wrote:

What you want to do is a full floater axle. Don't try and bend the housing or anything Jerry Rigged like that. Your AE86 is way too nice to do a hack job.

Either way works. Cutting or bending has been done for years and doesn't cost $1100 in parts alone.

If it didn't work, nobody would have done it.

I love how this is considered "Jerry rigged" but using rusty, scrap battery trays from E30's to trunk mount batteries is "Grassrooots" when you can buy a proper battery mount for less than $100.00

Some days you guys really amaze me.

Good luck with your Corolla, it looks badass :)

Shawn

grassroots is in the eye it seems - to some it is 335i and others it has to be Miata.

Trans Am cars of old did the heat and bend....

I like all options
Dec. 14, 2008 2:38 p.m. blaze86vic New Reader

In reply to Trans_Maro:

I call it Jerry Rigged because it causes wear issues on the diff and splined end of the axles. For the rest of the solid axle world this is a moderate concern, but for the Toyota 6.7" solid axle world, this is a big concern because the axles are pretty weak. So adding un-necessary stress is not desirable.

I'm all about doing things on the cheap, but I'm about doing it right as well. The only reason spec race cars use bent axle housings is because it's the only way to have rear camber and still be within in the rules. Floater axle setups are not allowed in almost any spec racing leagues.
Dec. 14, 2008 2:55 p.m. Trans_Maro New Reader

Hmm..

Guess you missed the part where I used a Starlet axle huh?

It's not like there aren't hundred of thousands of these axles in the world, the same unit was used in the TE series coil-sprung Corolla and an upgrade to a Celica Supra diff is easy enough and probably gains as much weight as the floater kit does.

A floater still skews the shaft in the housing. It just gives you a second set of splines so you have even more room to move the flange end of the axle around. Granted, there will be less potential for wear because of the extra freeplay from two sets of splined connections but it's not like there's a CV joint in the shaft allowing for articulation.

A full floater takes stress off the axle shafts because the weight of the vehicle is now carried by a spindle instead of the axle shaft itself. Now the shafts only have to do one job (transmit power) instead of two (transmit power and carry weight).

Have YOU actually done this modifcation or are you just regurgitating second-hand info that you heard somewhere?

See you on the track!

Shawn
Dec. 14, 2008 5:15 p.m. ae86andkp61 New Reader

We bent the housing on our LeMons TE Corolla last year and have had no problems so far. Granted, it is behind a 3T-C with a very mild bit of tuning, not a turbo 4A-G, and we were using GT-S center sections with 195/60-14 Hankook RS-II or Azenis in the same size, not R-comps or slicks, so YMMV.
Dec. 14, 2008 6:57 p.m. kevlarcorolla New Reader

In reply to ae86andkp61:

Do you know how much camber was acheived?.

Thanks for all the replies guys,here's the thing-I'm not able to afford about $1500 in parts(I'm canadian,so dollars down plus shipping)plus I notice the itty bitty brakes for the dwarf,not so good for a 200whp 1800lb car me thinks. I have a complete miata and the plan is to swith the corolla over to a-arms all around but no time this winter,this is kind of a short term bandaid deal.
Dec. 14, 2008 7:02 p.m. blaze86vic New Reader

I'm not up for pissing matches from you Maro man, so you can save it. I simply stated why a floater axle is more desirable on an AE86. And yeah, there are ton's of these axles for other cars, but AE86's use a different axle bearings that is $100 per bearing, and every time you break an axle you need a new bearing, so it gets expensive fast.
Dec. 14, 2008 7:40 p.m. aussiesmg HalfDork

Mazda LSDs are rare in OZ so I used a Alfa GTV solid rear in my RX3. Point is I raced it for 5 years 35 weekends a year and to three state titles with a rear end bent to gain 3/4 of a degree of negative camber with absolutely no problems or axle/bearing failures.

This is my personal experience.
Dec. 14, 2008 9:04 p.m. joey48442 Dork

I guess I don't understand this, maybe someone can explain...I thought the only way negative camber could work is with an IRS...I thought that as the body leaned outwards in a corner, it squared the outboard tire up with the road. Now, I thought that with a solid rear axle, the tires were always square with the road? (Unless the car is rolling over...) So wouldn't bending a solid rear axle to gain some negative camber be counterproductive? As in the only way for the tire to now completely touch the ground, the tire on the inboard side would have to leave the ground? I don't get it.

Joey
Dec. 14, 2008 9:23 p.m. kevlarcorolla New Reader

joey48442 wrote:

I guess I don't understand this, maybe someone can explain...I thought the only way negative camber could work is with an IRS...I thought that as the body leaned outwards in a corner, it squared the outboard tire up with the road. Now, I thought that with a solid rear axle, the tires were always square with the road? (Unless the car is rolling over...) So wouldn't bending a solid rear axle to gain some negative camber be counterproductive? As in the only way for the tire to now completely touch the ground, the tire on the inboard side would have to leave the ground? I don't get it.

Joey

You are sorta right,the tire is essentially square to the road,unless the inboard wheel goes over a bump,then the outboard wheel goes positive camber the same amount as the inboard will go negative.Or if the body rolls excessively and the links bind and axle follows the body lifting the inside rear.The real problem is radial tires generate max grip with negative dynamic camber so the inside edge of the tire generates a touch more heat then the outside shoulder. If the solid axle was the hot ticket all race cars would run solid front and rear right?.
Dec. 14, 2008 11:47 p.m. joey48442 Dork

kevlarcorolla wrote:

joey48442 wrote:

I guess I don't understand this, maybe someone can explain...I thought the only way negative camber could work is with an IRS...I thought that as the body leaned outwards in a corner, it squared the outboard tire up with the road. Now, I thought that with a solid rear axle, the tires were always square with the road? (Unless the car is rolling over...) So wouldn't bending a solid rear axle to gain some negative camber be counterproductive? As in the only way for the tire to now completely touch the ground, the tire on the inboard side would have to leave the ground? I don't get it.

Joey

You are sorta right,the tire is essentially square to the road,unless the inboard wheel goes over a bump,then the outboard wheel goes positive camber the same amount as the inboard will go negative.Or if the body rolls excessively and the links bind and axle follows the body lifting the inside rear.The real problem is radial tires generate max grip with negative dynamic camber so the inside edge of the tire generates a touch more heat then the outside shoulder. If the solid axle was the hot ticket all race cars would run solid front and rear right?.

I guess if all tracks were perfectly smooth, a solid axle would be best. I see your point though.

Joey
Dec. 15, 2008 8:32 a.m. blaze86vic New Reader

Don't forget, that the key reason for camber is to counter act the effect of tire roll. As you stress a tire in a turn the tire will roll under it self. Here is a simplified figure out of the Race Car Vehicle Dynamics, book by Millikan & Millikan.