davidimurray
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| posted on 7/5/16 at 08:12 PM |
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Twitchy Handling
Been out for a spin today while the weather was nice (which ended with a massive rain storm and a rather treacherous plod along semi flooded
roads!)
One complaint about my car is as the speed builds, the car becomes more and more twitchy/nervous, requiring lots of driver input and particularly bad
on bumpy roads. My first thoughts were bump steer, but on first view the trackrods look horizontal. I need to jack the car up check it properly
through the range of movement. Tied in with this concern though, since I fitted the Duratec instead of the Pinto, I am prone to tyre squeal under
breaking or turning a corner while hitting a bump. I am wondering if I need softer springs at the front. Currently 350lbs front and 250lbs rear (Car
is a Haynes Roadster).
anyone have any thoughts
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daniel mason
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| posted on 7/5/16 at 08:19 PM |
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How stiff is the damping?
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davidimurray
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| posted on 7/5/16 at 08:20 PM |
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Need to double check, but from memory it is wound in 3 clicks of the 12 available
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daniel mason
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| posted on 7/5/16 at 08:31 PM |
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3 clicks clockwise from fully anti-clockwise? So at the softer end of adjustment?
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CosKev3
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| posted on 7/5/16 at 08:33 PM |
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What tyres and pressures are you running?
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davidimurray
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| posted on 7/5/16 at 08:41 PM |
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I think they are at the softer end - will double check in the morning.
Tyres are Toyo T1Rs, running at 18PSI
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CosKev3
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| posted on 7/5/16 at 08:50 PM |
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T1R's are only really a mid range tin top tyre,I would guess that's where your tyre squel is coming from.
They are a harder compound rubber to give better wear.
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SJ
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| posted on 7/5/16 at 09:04 PM |
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you can't tell bump steer from looking. Get a laser pointer and check it properly.
It's pretty easy to do.
Stu
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wylliezx9r
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| posted on 8/5/16 at 12:43 AM |
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I would have a play with the track rods. Do a couple of turns one way, then try the car out if it makes it worse go the other way, that's how I
set mine up. Got it perfect in about 20 minutes. No science just trial and error.
Edit to say if your front springs are too stiff it shouldn't result in the symptoms you're having.
[Edited on 8/5/16 by wylliezx9r]
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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Ben_Copeland
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| posted on 8/5/16 at 04:27 AM |
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Try switching the springs round. 350 on the back 250 on the front.
The rear shocks are at a steeper angle so require the higher poundage.
If it's anything like mine the car should be 50/50 balance in weight near enough anyway.
Try it, also soften you shocks a bit if they bang on bumps. Having your suspension 'tuned' will make a massive difference to the handling
as well
[Edited on 8/5/16 by Ben_Copeland]
Ben
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britishtrident
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| posted on 8/5/16 at 08:02 AM |
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Twitchy handlling in a straight line and excessively squealing tyres litterally screams a geometry related issue --- bump/roll steer or toe-setting
(front and rear) or ackerman.. The squeal will be generated by the lightly loaded inside front wheel literally getting dragged at an excessive slip
angle by the domminant more heavily loaded outside front wheel.
First step is to check front and rear toe setting -- all wheels should a have a small ammount of toe-in when the car is loaded as normally driven.
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MikeRJ
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| posted on 8/5/16 at 08:03 AM |
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quote:
Originally posted by davidimurray
My first thoughts were bump steer, but on first view the trackrods look horizontal.
The angle of the track rods doesn't tell you whether the basic geometry is correct. If the steering rack is too long or too short then you can
get still get bump steer, though you can minimise this by moving the rack mounting location.
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MikeRJ
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| posted on 8/5/16 at 08:11 AM |
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quote:
Originally posted by CosKev3
T1R's are only really a mid range tin top tyre,I would guess that's where your tyre squel is coming from.
They are a harder compound rubber to give better wear.
They are a perfectly good tyre, though the sidewalls are a bit soft for heavier cars. They are as grippy as many premium UHP tyres in the dry but
don't tend to last as long so I'd say the rubber is pretty soft if anything. In 195/50R15 they offer exceptional value.
As BT says, tyre squeal is almost guaranteed to be geometry related. I changed the steering rack on my tintop earlier this year and the tyre squeal
was horrendous under hard cornering (Contintal Sportcontact 5) until I had time to get a full alignment done.
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davidimurray
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| posted on 8/5/16 at 08:34 AM |
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Thanks for the advice everybody.
Before I fitted the Duratec the tyres never squealed like they do now - that was without any suspension/geometry changes.
I have recently checked and corner weighed the car. I recently checked the geometry and based on what others are running I have -
0 Toe at rear
2 deg toe in front
1.75 deg camber
F to rear weight distribution is 46:54
Cross corner weights are within 3kg
Ride height is 20mm higher rear than front
The tyre squeal does not occur during cornering, but when braking in a straight line over bumps, as if the front end is skipping.
I have heard of some people putting a little toe out on the front so if the bumpsteer does not show anything obvious that might be the way forward.
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CosKev3
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| posted on 8/5/16 at 09:00 AM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by CosKev3
T1R's are only really a mid range tin top tyre,I would guess that's where your tyre squel is coming from.
They are a harder compound rubber to give better wear.
They are a perfectly good tyre, though the sidewalls are a bit soft for heavier cars. They are as grippy as many premium UHP tyres in the dry but
don't tend to last as long so I'd say the rubber is pretty soft if anything. In 195/50R15 they offer exceptional value.
As BT says, tyre squeal is almost guaranteed to be geometry related. I changed the steering rack on my tintop earlier this year and the tyre squeal
was horrendous under hard cornering (Contintal Sportcontact 5) until I had time to get a full alignment done.
As I said,a mid range tin top tyre.
If you try them against premium tin top tyres (michelin/Dunlop etc) you will see they are not a patch on them.
The wear rating on them is 300 iirc,on a light weight kit car you don't need anywhere near that sort of wear rating.
The improvement you get going to mid compound tyres from tin top road tyres on a kit car is massive,even the harder wear rating 180 ns2r's
I'm running.
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CosKev3
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| posted on 8/5/16 at 09:05 AM |
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quote:
Originally posted by davidimurray
Thanks for the advice everybody.
Before I fitted the Duratec the tyres never squealed like they do now - that was without any suspension/geometry changes.
I have recently checked and corner weighed the car. I recently checked the geometry and based on what others are running I have -
0 Toe at rear
2 deg toe in front
1.75 deg camber
F to rear weight distribution is 46:54
Cross corner weights are within 3kg
Ride height is 20mm higher rear than front
The tyre squeal does not occur during cornering, but when braking in a straight line over bumps, as if the front end is skipping.
I have heard of some people putting a little toe out on the front so if the bumpsteer does not show anything obvious that might be the way forward.
I've recently had mine set up,from what the average seemed to be:
1mm toe in rear
1deg negative camber rear
1mm toe in front
1.5mm neg camber front
Mine now handles really nicely.
Although I think alot of my improved suspension feeling is down to fitting new bushes with stainless tubes and making sure they all move freely, on
the original mac1 bushes I had a lot of very tight bushes that took a lot of effort to move the wishbones 
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davidimurray
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| posted on 8/5/16 at 09:21 AM |
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quote:
Originally posted by CosKev3
quote:
Originally posted by davidimurray
Thanks for the advice everybody.
Before I fitted the Duratec the tyres never squealed like they do now - that was without any suspension/geometry changes.
I have recently checked and corner weighed the car. I recently checked the geometry and based on what others are running I have -
0 Toe at rear
2 deg toe in front
1.75 deg camber
F to rear weight distribution is 46:54
Cross corner weights are within 3kg
Ride height is 20mm higher rear than front
The tyre squeal does not occur during cornering, but when braking in a straight line over bumps, as if the front end is skipping.
I have heard of some people putting a little toe out on the front so if the bumpsteer does not show anything obvious that might be the way forward.
I've recently had mine set up,from what the average seemed to be:
1mm toe in rear
1deg negative camber rear
1mm toe in front
1.5mm neg camber front
Mine now handles really nicely.
Although I think alot of my improved suspension feeling is down to fitting new bushes with stainless tubes and making sure they all move freely, on
the original mac1 bushes I had a lot of very tight bushes that took a lot of effort to move the wishbones
Can I just check - you say 1mm toe in, is that across the wheel and if so what diameter wheel is that 1mm of toe across? If it is 1mm across 15"
then that works out as 0.15deg toe in
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CosKev3
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| posted on 8/5/16 at 09:29 AM |
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I don't really understand the way you set them up!
I just looked at various threads on here and Internet, most new equipment now uses mm rather than degrees apparently so I just asked the bloke setting
it up to do it 1mm toe in on each wheel.
Sorry I don't know how this converts over to degrees.
But I am running 15 inch wheels yeah.
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CosKev3
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| posted on 8/5/16 at 09:32 AM |
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http://westfield-world.com/Pix/susp/westy_bottom.jpg
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furycossiesteve
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| posted on 8/5/16 at 02:59 PM |
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IMHO T1Rs are useless on a kit car/7/Fury etc.
I had them on my Fury and they were dreadful I put R888s on, totally transformed the car.
I see you are in South Wales. If you have trouble with set up the guy you need to speak to is Dave Gallop across the bridge and near Castle Combe.
Google Track Developments. If he can't sort it no one can.
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Doctor Derek Doctors
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| posted on 8/5/16 at 05:01 PM |
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2 deg of toe is alot. First job should be to correct that to 1mm
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adithorp
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| posted on 8/5/16 at 07:27 PM |
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quote:
Originally posted by Doctor Derek Doctors
2 deg of toe is alot. First job should be to correct that to 1mm
Agreed, 2deg is a lot. I'd expect anything between 10-30' to be a good starting point.
(1mm will be somewhere between 10-15' depending in rim diameter.)
"A witty saying proves nothing" Voltaire
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davidimurray
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| posted on 8/5/16 at 08:30 PM |
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Thanks everybody for the advice. I wound out some of the toe in I had today and the car felt better. I will do some proper checks and reduce the
toe-in. I am also going to check the bump steer and see how much I have.
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laurencedawson
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| posted on 23/6/16 at 01:19 PM |
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Hi guys,
I have a tiger Avon, used for Trackdays only,
Using the same tyres you have.
You can only really know if you have the right tyre
Pressures by measuring the tyre temp after a run.
Measure inside, middle and outside across the tread on each tyre.
You can pickup an infra red temp sensor for about
£20 from demon tweeks.
The average of the inside and outside temps should be
The same as the middle reading. That tells you that the
Pressure is correct.
If you then have a big difference between outside
And inside, it gets more complicated!!
Could be camber, toe or just the circuit layout.
Contrary to most advice, we ended up at about
27psi with those tyres, higher Tha most reccomend...
Les
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