Toe-in and bump steer

[Uboat]

Hello,
I understand my car has way to much toe-in on the front suspension, and I need to fix this. Although the workshop manual gives no hint of this, I understand from other threads that this can be fixed by adjusting the steering.

How do I measure the toe-in on my car, what kind of gauges do I need and how do I adjust to the correct toe-in (what is the correct toe-in for my 1974 Elan +2?)?

Also,
I notice bump steer, how do I fix this?

I would be much helped if any of you experts could give me some instructions
/Ulf

[leifanten]

Toe in is the difference in the distance between the rear center of the tire and the front center of the tire. It should be between zero and 4.76mm. You need a reasonably accurate (very long) caliper gauge to measure these two distances and make required changes by turning the steering ball joints out or in (in equal whole turns on either side) until the measurement is the right one. I made my caliper by a broomstick with two fixed bolts at a fixed distance, and measure the gap between the bolt and the tire at each side with a ruler.

[leifanten]

Bump steer is taken care of by shims under the steering rack mounts. Mine has four shims of heavy gauge (0.8mm) sheet metal.

[mikealdren]

Ulf,
There are threads on the forum about setting the shims under the steering rack to minimise bump steer, have a search and see but get the toe in right first. You can set it yourself but all tyre fitters also have accurate gear to set it.

Mike

[john.p.clegg]

Mike
If only they had data for pre 21st Century vehicles,and even then would I trust the spotty herberts at XXXXXX,XXXXXX or even XXXXX...?

I don't think so...

John

P.S. no disrespect to anyone called Herbert!

[bcmc33]

You can set it yourself but all tyre fitters also have accurate gear to set it.

I have an issue here regarding modern tyre fitters accurate gear - they are laser driven and only measure wheel angle for modern vehicles - not actual dimensions as specified for our old cars.

[jimj]

Whoever XXX is, I`ve used that tyre place (name?) on the right coming out of Buxton on the A6 towards Chapel, to have my tracking checked. I`ve found them very helpful and conscientious. They do have data for the Elan though I took the info. with me. I had done it myself with 2 bits of wood, a pencil and a rule but their, somewhat more sophisticated equipment showed my measurements to be 2 mm out, hardly surprising.
Regarding bump steer; this is even more difficult to calculate for the average owner and, like all suspension/steering settings, the accuracy is crucial to getting the most enjoyment from your car. Spend a few ?s and have it done right is my advice.
Jim

[john.p.clegg]

Jim

After they corrected your 2mm could you tell the difference?

John

[bcmc33]

How would you check the bump-steer settings with the body on the chassis?

[prezoom]

Setting bumpsteer accurately is time consuming and takes a bit of equipment you will have to make, but it can be done at home.

You will two dial indicators, a plate 10mm thick, 20cm high and about 55cm long, but not so long that it will foul on the inside of the wheel well. For bolt on wheels, drill or machine a hole in the center of the plate, large enough to clear the front hub. Then drill four holes to match the wheel studs. The four holes for the wheel studs can be in any plane as the hub rotates. The plate must fit up against the plane of the surface of the hub. Knock on hubs will require a little different method of securing the plate to the hub. Construct a fixture to hold the dial indicators, mounted horizontally so that the tips of the indicators are 2 or 3cm inboard and will rest just inside each of the outer ends of the plate. The fixture should hold the indicators at line drawn through the center of the hub at ride height. You can get away with just one dial indicator by replacing the other with a stud with a smooth rounded end fixed to one end of the fixture about the same length as the indicator sticks our from the fixture. Both the stud and the indicator must contact and ride against the moving plate when doing the measurement.

Block the chassis at ride height, remove the front wheels and corresponding front dampers/springs. Of course the anti-roll bar will be disconnected as well. Bolt the plate to the hub so that the plate is horizontal to the ground, and secure the hub from being able to rotate. Set the fixture with the dial indicators up against the plate, with the indicators slightly depressed and set the indicators to zero. Use a trolly jack or some other means to be able to raise the front suspension through its arc for approximately 8cm of droop and bump. You will be doing one side at a time.

By marking the plate with a line through the center of the plate from end to end and then sufficient markings both above and below this line at the outer edges, you will have a reference points when raising or lowering the front suspension. Be sure to set the dial indicators at the center line of these markings, a direct line through the center of the hub. While lowering and raising the front suspension from ride height, note the differences in the readings on the dial indicators. This distance should be about 8cm above and below the center line. Any difference in the measurement from zero, will be the amount of bump steer. This measurement can be brought closer to zero by raising or lowering the mounting points of the steering rack. Believe me, a rack and pinion is very easy compared to other types of steering.

An easy method of setting toe is with two pieces of wood approximately 55cm square and 2cm to 3cm thick. Cut two slots in each board, one on each edge. With the boards stacked on top of each other, the slots should be cut approximately 25cm above the lower corners of boards parallel with the bottom edge. The slots shoud be 25cm to 40 cm deep, equal on each board. Lean each board up against the front tires and block them so they are in complete contact all around the tires. Then using two tape measures, slip them in the slots from one side to the other. The difference in measurement will be difference between the front and rear outer edges of the tire. Half the distance measured will be the amount of toe in or out. Adjust as required with the tie rod ends being screwed in or out. Be sure to have the steering wheel centered and make the adjustments in equal amounts on each side to keep the wheel centered.

I believe it is best to set the toe, then do the bump steer and then when finished with the bump steer, go back and check the toe again.

Rob Walker
26-4889

[Uboat]

Ok thanks,

I found the part mentioning adjustment of toe in the workshop manual.

I understand that the accuracy of the measurement of the toe is critical. Then for starters, how do I know that the steering is perfectly centered? For sure, I can not trust the position of the steering wheel...
/Ulf

[csjohnson]

Just buy a set of toe plates that are not that expensive. I do not know where to get them in the EU but here you can find them hear.

http://www.speedwaymotors.com/Longacre- ... s,502.html

You can also get a bump steer gauge from them.

http://www.speedwaymotors.com/DECO-BUMP ... ,2703.html

Chris

[paddy]

I used a cheap DIY line laser with a magnetic base which just attaches to the brake disc, a bit like this one:

http://www.toolspot.co.uk/product/toolz ... -generator

(This is not a product recommendation as I haven't used this specific model.)

The very cheap ones are not really accurate enough for absolute measurements (ie actually setting the toe-in) but perfect to see the toe-in change as you move the suspension up and down and check each side in a few seconds. Cheap enough that you can fit one to each side, and adjust the rack shims very easily. For me it took a couple of hours to do all the adjustment - the time-consuming part is removing the rack mounts each time and changing the shims.

Paddy

[john.p.clegg]

Paddy

....and the further away the "target" is ,the more accurate the setting...

John

[leomartin6]

Nice post. good to hear that.