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#1 shyfd

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Posted 30 September 2011 - 06:17 PM

I have recently got my Vtec kit on the road and am struggling with alot of bump steer, so much so that I can't drive her until its sorted.

I read some older posts about racks andmaing sure the track rod arms are straight. I need to work out if I need to buy a new rack.

The rack that came with my half built project is a NAM5058 from Mini Sport

http://www.minisport...fo_NAM5058.html

Is this good enough do you think I should I get new sports pack one? And wheres the best place?

Also did making the track rods straight help at all in the end?

Thanks

#2 rustandoil

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Posted 01 October 2011 - 07:16 AM

Changing the rack wont make a difference surely? the Sportspack rack is the same as the standard rack but has limited movement to prevent 13 inch wheels rubbing on the shell.

Are you using the Z-Cars front subframe?

#3 andream88

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Posted 01 October 2011 - 02:22 PM

Page 34 of cptkirk's thread.

I have the same issue.
You need rose jointed track rods to solve the issue...

#4 cptkirk

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Posted 03 October 2011 - 07:58 AM

Page 34 of cptkirk's thread.

I have the same issue.
You need rose jointed track rods to solve the issue...



Here's the problem, not only do the cars suffer from bump steer but because of the bigger 13" wheels the scrub radius around the kingpin is also massive. The scrub radius is what makes it feel like the steering wheel is being ripped out your hands on things like un-even surfaces and cats eyes. Unfortunately there's nowt we can do about the scrub radius so you're just gonna have to put up with that side of things, however in an effort to make things feel better we can attempt to alleviate some of the bump steer by using rose joints and spacers.

Some people on here have just replaced the normal track rod end with a female thread rose joint and as yet I have not heard of any failures so we can assume that this is a tried and tested way of dong it. I went a bit further with mine having bits machined that may have been unnecessary from a cost point of view but I felt happier having more thread covered on the set up.

All rose joints were purchased from McGill Motorsport, along with misalignment spacers, they also sell on ebay and are sometimes cheaper on the bay.

Imperial nuts and bolts were sourced locally at a good old fashioned machine shop but you can get them off ebay.

Cooper S steering Arms & Sportspack Rack were sourced from Minisport.

All of the information from my build can be found in my build diary in posts 532, 533, 539, 544 & 547

You might need someone to machine a spacer to go between the rose joint and the track rod arm - going from memory I think mine was 35mm, dont forget to get one end turned so it doesnt interfere with the rose joint as the suspension rises and falls.

Edited by cptkirk, 03 October 2011 - 07:59 AM.


#5 rustandoil

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Posted 03 October 2011 - 08:30 AM

Do you think that set-up would get through IVA? i am hoping to avoid IVA but am still building my car with it in mind

#6 cptkirk

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Posted 03 October 2011 - 09:48 AM

I am unsure, however its not the end of the world to swap it over for the test.

#7 R1mini

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Posted 03 October 2011 - 10:01 AM

I assuming your all using the standard front subframe if you are having bump steer issues?

As for scrub radius, wheels that have less offset will help, unless you have to run those particular wheels for a reason

Cheers
David

#8 cptkirk

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Posted 03 October 2011 - 11:01 AM

I assuming your all using the standard front subframe if you are having bump steer issues?

As for scrub radius, wheels that have less offset will help, unless you have to run those particular wheels for a reason

Cheers
David


I agree that you could use a smaller offset to help with scrub radius but as to how much less an offset I couldnt say without having a measure up bits that are in the way.

I am running a Zcars front subframe, even though the steering rack has been moved it still had angled rod arms, hence the need for a spacer or more drastic is to move the steering rack to a more suitable position, lessening the angle to the steering arms.

#9 R1mini

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Posted 03 October 2011 - 01:57 PM

I've no idea how much less offset would make the car better to drive, it can't be down to each person to experiment, Zcars I hope would give some baseline figures to work with, but with the mini, less offset and reasonable sized wheels are the way to go.

I thought the primary idea of the tubular front frame was to reduce the bump steer to almost zero, that is what I was led to believe, the version I had used the standard location for the steering rack and the later versions mounted the steering frame on the tube frame to further improve the geometry. From what people are saying that doesn't appear to be the case

David

#10 shyfd

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Posted 11 October 2011 - 07:36 PM

Think I have sorted the bump steer now. As suggested I changed track rod ends and added a35mm spacer to make the arms level.

These are all the parts I used if anyone else needs them.

Spacer

http://www.ebay.co.u...984.m1439.l2649

Rose Joint

http://www.ebay.co.u...984.m1439.l2649

Bolt

http://www.ebay.co.u...984.m1439.l2649

Missalignment spacer

http://www.ebay.co.u...984.m1439.l2649

Nut

http://www.ebay.co.u...984.m1439.l2649


Next on to my other issue's

knocking rear suspension and swaying at high speed (scary)

#11 andream88

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Posted 11 October 2011 - 07:39 PM

any pics of the finished work mate?

#12 cptkirk

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Posted 12 October 2011 - 07:56 AM


Next on to my other issue's

knocking rear suspension and swaying at high speed (scary)


Ah ha - someone else with high speed sway - do you find this more when changing gear/sudden let off?

I have yet to prove it but I am pretty sure that the rear suspension knocking I am getting is from the wrong size bolt in the rose joint and in 1.5 weeks I will be able to say one way or the other when I take my engine out as I will be getting my digital vernier on the parts in question.

Top job on the ordering of the bits for bump steer alleviation. One thing you might need is a 1/2" UNF half nut to tighten up against the rose joint on the steering rod arm, although you might be able to use the non-nylock nut that will be spare from the nut and bolt set ordered.......

I take it that you have go the Cooper S arms on the car also? If you havent I suggest that you get them also as they are far superior to the standard item.

If you find a fix for the high speed sway in the meantime I would love to know what it is.

Andy

#13 shyfd

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Posted 12 October 2011 - 08:15 PM



Next on to my other issue's

knocking rear suspension and swaying at high speed (scary)


Ah ha - someone else with high speed sway - do you find this more when changing gear/sudden let off?

I have yet to prove it but I am pretty sure that the rear suspension knocking I am getting is from the wrong size bolt in the rose joint and in 1.5 weeks I will be able to say one way or the other when I take my engine out as I will be getting my digital vernier on the parts in question.

Top job on the ordering of the bits for bump steer alleviation. One thing you might need is a 1/2" UNF half nut to tighten up against the rose joint on the steering rod arm, although you might be able to use the non-nylock nut that will be spare from the nut and bolt set ordered.......

I take it that you have go the Cooper S arms on the car also? If you havent I suggest that you get them also as they are far superior to the standard item.

If you find a fix for the high speed sway in the meantime I would love to know what it is.

Andy



Yes I already used the nut that came with the bolts I ordered.

Regarding the "high speed sway", Its exactly as you discribe when letting off or changing gear. At first I assumed it was the lorry ruts that I was moving in and out of but it seems to do it on new roads aswell. Do you have any ideas on what causes it?

I still need to get the camber and toe checked again on the back as the garage I used didn't seem to like the idea of working for thier money.

As for the noisey suspension, It seems to be after a bump like when the suspension will have rebound fully and reach its full length.(if that makes sense).
Think i will check the bolts aswell before I spend too much time looking at it.

#14 cptkirk

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Posted 13 October 2011 - 04:04 PM


Regarding the "high speed sway", Its exactly as you describe when letting off or changing gear. At first I assumed it was the lorry ruts that I was moving in and out of but it seems to do it on new roads aswell. Do you have any ideas on what causes it?


The physical cause is the weight transfer back onto the front wheels as the car goes from acceleration into deceleration, as to the mechanical cause I am at a loss right now but will be looking more into it.

I am purely guessing when I say that it MIGHT be some bump steer as the rear stops squatting under acceleration (with the front rising slightly), the front end then dips under deceleration causing the tracking to move from a possible toe out under acceleration to toe in under deceleration.

Mine has been better since sorting my steering out, once I get to the rear arms and sort the slack in them I hope it will be better still but we will see.

If anyone with greater suspension knowledge wnats to give some input please feel free as swaying around when changing at around 100mph isnt a nice feeling and I personally would love to stop it happening

#15 shyfd

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Posted 13 October 2011 - 06:04 PM

Ive checked the rear swing arm mounting bolts and rose joints. Both seem to match there abouts at 1/2" (12.7mm)

Next will check the shock itself....

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