Dave_KE30

Video Of Corolla Suspension In Action On Track

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Hey Fellow Racers,

 

I recently shot a view from under my KE30 whilst at the track; I though some of the suspension nerds might find it interesting (me included!). There's so many little features in the footage that you just don't see from in-car video: watching the tyre contact patch, the amount of tyre deflection, suspension travel, body roll ect. From this I found some obvious ways I can improve the grip of the car through the corners, check it out:

 

 

Circled in the picture below is where the (poor) camera was mounted. The lens on the case ended up smash haha, but that happened in the paddock and not on track.

post-21253-0-76170000-1456394365_thumb.jpg

Edited by Dave_KE30

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That was really fascinating. Should be compulsory viewing for anyone trying to stuff massive tyres or stupid offset/spacers under their guards etc. The tyre deflection was quite striking, and the compromise of camber.

 

So what are the ideas you have come up with?

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Important to note the sidewalls doing a lot of work on the rear, and you can imagine how rigid stretched tyres can become and not grip like they should. I think the inside front wheel had a reasonable contact patch, more so because it was very flat on the road when it was on the outside so you're probably not going to scrub your outer edges off, and that's the main concern I think. Did they wear evenly?

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Thanks for the comments!

 

Tyre wear is pretty bad on the outside edge to be honest. From the wear it looks like the outside quarter of the tyre is doing a lot of work, and the next quarter toward the inside is being bulged out by the lateral force and wearing this into a low spot. Tyre temps show the same, much hotter on the outside edge. Oh and hot tyre pressures are as optimal as I can get them based on tyre temps using the current settings.

 

post-21253-0-84452700-1456505791_thumb.jpg

 

Anyway, the photo below was after three or four events with regular front to back rotations, after this (and replacing the flat spotted tyre haha) I had the tyres flipped on the rims to even out the wear. The only other thing which might cause the inner section to wear could be toe settings, but I don't think this is it.

 

post-21253-0-72811200-1456508212_thumb.jpg

 

The conclusion is to me is: more camber required on the front. And I think the video proves this as well, particularly the way the tyre scrubs clean at the first corner, the outside edge rubs clean first around the corners.

 

Unfortunately I can't get more camber out of the strut top, and can't lengthen the LCA within the standard front guards, so probably some fender flares or maybe some major guard rolling is required. I have some KE20 LCA that I can put in which should add 25mm track each side and go from 0.7 degrees camber (max adjustment) to 1.0-3.5 degrees (min/max adjustment). At a guess, about 2.5 degrees might be optimal?

 

Plus with some flairs I can run some more caster which should help with dynamic camber. Also I plan to raise the front roll centre height which should help to reduce some of the body roll force and so the front roll bar can be softened which should help the inside front tyre contribute more to the cornering grip and provide some camber gain by angling the LCA up a bit more at static ride height.

 

Does that sound logical? Any other ideas?

 

Dave

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I wasn't going to bother about this, but here is the front suspension. Next time I will look at making a proper bracket so I can see more of the tyre but zip-tied to chassis worked ok this time haha. Gives a good idea of the range of travel and the change in LCA angle (and roll centre implications).

 

Dave

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No rca's?

 

This thread it's rather interesting for me re tyre deflection as I'm just about to fit my new coilovers and am a bit concerned about the amount of clearance I have off the adjuster rings. Currently have 195's stretched over 9's but really want to go 205's on the front.

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Here's a couple of pics of my clearance. Note I haven't yet set a definitive ride height on the base adjustment so this may change a bit yet, hopefully may only need to go up so that will give me a bit more clearance.

 

post-1315-0-60296300-1456786190_thumb.jpg

post-1315-0-69708400-1456786236_thumb.jpg

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Haha Taz_Rx, that is a good question, my answer is a little bit embarrassing: At the front I've got about 2mm/3mm between the tyre and the coilover perch - I can't even get the ratchet strap webbing around the tyre to secure the car on the trailer! What strut are you using Taz_Rx?

 

I run a 15"x7" rim +20 offset with a 225/50R15 tyre and a 6mm spacer up front. So far it hasn't been an issue, but if the tyre ever made contact with the coilover perch it would actually unwind the perch lock nut and it would spin down further into the tyre/wheel; catastrophic! Would I recommend it... probably not, but it hasn't been a problem so far (hundreds of laps). Eventually though I hope to get more clearance here becase different tyre brands could cause an issue. There are some different types of coilover perches as well which could offer more clearance, l like the T3 ones that use a pinch bolt instead of a lock nut.

 

I suspect the rear tyre deflects more than the front because the live axle hold the tyre normal to the bitumen, whereas the front is influenced by camber, toe, caster and steering angle which artificially push the tyre away from inward deflection.

 

Something else to consider from the video is that these are R-compound tyres and they grip significantly more than any road tyre (at least in my experience), and the carcase construction is slightly different, so a road tyre might behave differently. Maybe even differet brands of semi-slick might behave different too; these are Kumho V70a which I've found to be a bit faster than Toyo RA1 or the previous model Yokohama Advans.

 

Some evidence of rubbing on the coilover perch:

post-21253-0-61811300-1456838667_thumb.jpg

Calculated clearance before getting wheels made:

post-21253-0-08905100-1456838791_thumb.jpg

Actual clearance:

post-21253-0-21294800-1456839370_thumb.jpg

 

Dave

Edited by Dave_KE30

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No rca's?

 

This thread it's rather interesting for me re tyre deflection as I'm just about to fit my new coilovers and am a bit concerned about the amount of clearance I have off the adjuster rings. Currently have 195's stretched over 9's but really want to go 205's on the front.

 

I reckon you could go a 205 no problem if a 9 inch rim fits at the front, just use a shorter spring so the perch is further from the tyre. The height of your lower perch will depend on your spring rate, corner weight, desired ride hight and the amout of travel you want. I think 2 inches of compression and 3 inches of droop would be enough for most sporty cars (firm springs and swaybar). Use a tether strap or tender spring to keep the main spring captive on droop if your main spring is too short for the shocks travel at the desired ride height. Hopefully your tyre clearance will be better than mine.

 

On my car I could get rid of the tender spring it would drop the car 20mm, so I could adjust the perch up away from the tyre. But then there wouldn't be enough droop to keep the inside tyre on the road at the current roll angle, which I think would be a loss. So I could run a shorter main spring, but then compression travel would only be about 54mm before the spring binds. Not may options!

 

post-21253-0-56571800-1456840430_thumb.jpg

 

Yeah no RCA's yet because the front roll centre calculated out to be ok-ish. I was actually going to do an adjustable inner pivot (at the cross member), instead. But now that am commiting to getting the car lower and wider I will have to get RCA's to fix the geometry. I actually tried negative offset RCA, but the car felt terrible, and with the new wheels and tyres the increased srub radius only gave me half a turn each way before the tyre hit the guards or body, and that was after love taps and an angle grider massage haha

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Yeah right, you have bugger all clearance. With a 205 I'm obviously going to get 5mm closer but wasn't sure how much deflection I might get. Good point about camber, steering angle etc resulting in not as much deflection compared to the rear.

 

Mine are shockworks base height adjustables for an 86. As i said before I won't get an accurate position of the (preload) adjuster rings until they're in the car and have weight on them. ..which will hopefully be tomorrow.

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Great vid tyre deflection is amazing!!! Did you have some sort of lighting on the camera?

 

Would be great to do the front vid as well .

 

nice work rob

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