fe1rx Installing Steering Rack Stops

[fe1rx]

Like many of you I have installed wider front wheels and tires on my 135i. In my case, Apex ARC-8 8.5 x 18 ET 45 wheels with 235/40R18 tires. These tires run very close to the strut tube and also rub on the chassis at the rear at full lock.



Although we don’t spend a lot of time at full lock, given the rub marks, it obviously happens. One way to eliminate this rub is to install stops on the steering rack. Turner Motorsports has an economically priced kit for this purpose, but I decided to build my own as I knew I would likely modify their length anyway.

https://www.turnermotorsport.com/p-3...op-kit/?pdk=BA

Like most cars, ours has Ackermann steering geometry, meaning the inside wheel turns more than the outside. This installing a stop will have a different effect on the inward turning wheel than the outer one.



The standard steering geometry provides maximum steering angles of approximately 41° on the inside wheel and 33° on the outside wheel and the steering wheel turns 3 turns lock to lock. As I have and AIM Solo DL installed in my car and able to access steering angle data, I was conveniently able to measure the correlation between stop thickness and steering range.

I fabricated my steering stops from Delrin, with a length of 10 mm and a light interference fit on the rack;



Removing the tie rod requires a 1.5” wrench. Torqueing it on installation requires either a crowfoot or a special tie rod tool. I had a 12-point crowfoot on hand but was surprised find that the tie rod uses an octagonal nut, not a hex, so the 12-point didn’t work. I ended up fabricating a crowfoot by welding socket to an old open-end wrench.

some reference marks on the outer tie rod before disassembling it makes it possible to reassemble things without upsetting the alignment.



For torques, I referred to the Bentley manual.



Removing the tie rod and installing the stops is uneventful.





After putting things back together, I measured the change at both the steering wheel and the wheels.

Lock-to-Lock (before/after): 3.0 turns / 2.6 turns
Inner Wheel Max Steer Change: -8°
Outer Wheel Max Steer Change: -5°

It also eliminates the previous slight interference I observed between the brake hose brackets at full lock and full droop. I now have positive clearance.

[houtan]

Thanks for the post and sharing the information. What brand tires are you using? I am running the same size tire same wheel but I thought the only rubbing I have is when the wheels are turned the tire rubs at the midpoint of the fender lip. I need to look at the chassis to see if it is rubbing there. I'm hoping my tire (sumitomo htr III) doesn't run as wide as the brand you are using.

[deesea]

This makes me concerned that my 18x9 ET45 wheels on 235/40/18 tires will never fit. I was hoping to run a set of bridgestone RE71Rs.

[fe1rx]

Originally Posted by houtan

Thanks for the post and sharing the information. What brand tires are you using? I am running the same size tire same wheel but I thought the only rubbing I have is when the wheels are turned the tire rubs at the midpoint of the fender lip. I need to look at the chassis to see if it is rubbing there. I'm hoping my tire (sumitomo htr III) doesn't run as wide as the brand you are using.

I have run RE-71R and Nitto NT01 in 235/40R18. I am not sure how they compare in terms of total section width or corner profile so I don't know which one is more critical with respect to rubbing.

[fe1rx]

Originally Posted by fe1rx

I have run RE-71R and Nitto NT01 in 235/40R18. I am not sure how they compare in terms of total section width or corner profile so I don't know which one is more critical with respect to rubbing.

8.5" ET45 fits like this. Your wheel will be 0.25" closer to the strut tube, which will probably mean you have to run a spacer to move it away a bit.

[ShocknAwe]

This is very cool. What is the impact on the turning radius with the rack stops installed?

[houtan]

Originally Posted by fe1rx

I have run RE-71R and Nitto NT01 in 235/40R18. I am not sure how they compare in terms of total section width or corner profile so I don't know which one is more critical with respect to rubbing.

Thanks. Do both the RE-71R and Nitto NT01 rub the chassis? Could the amount of camber or caster make a difference on where the tire ends up at full lock? I am at around 2.1 degrees camber and 10 degrees caster.

[fe1rx]

Originally Posted by ShocknAwe

This is very cool. What is the impact on the turning radius with the rack stops installed?

I estimate the turning circle will increase from 10.7 m (35.1 ft) diameter to 12.0 m (39.4 ft) diameter.

[fe1rx]

Originally Posted by houtan

Thanks. Do both the RE-71R and Nitto NT01 rub the chassis? Could the amount of camber or caster make a difference on where the tire ends up at full lock? I am at around 2.1 degrees camber and 10 degrees caster.

I am not sure if they both rubbed but I suspect so.

Good point about more negative camber making it worse. I run a bit of toe out up front, which would also make it worse. More caster would relieve things I think.

[zapatista]

Originally Posted by deesea

This makes me concerned that my 18x9 ET45 wheels on 235/40/18 tires will never fit. I was hoping to run a set of bridgestone RE71Rs.

Depending on your setup you might need 5mm or a little greater spacers in the front. I have 18x9 ET42 and the tube from my Koni Yellows and the inner wheel were rather "intimate."

Just saw fe1rx's response saying the same thing. fe1rx...I love your posts...thanks for all the experimentation and open posting about your process.

[bNks334]

Originally Posted by deesea

This makes me concerned that my 18x9 ET45 wheels on 235/40/18 tires will never fit. I was hoping to run a set of bridgestone RE71Rs.

7mm spacer at a minimum. My 255/40 RS3's are maybe 1mm off the strut with 17x9 ET45 (7mm spacer = ET38). 255 slicks would probably require a bit more spacing to keep the tire off the strut.

235 might fit, but why even bother with 9in rims if all you want to run is 235?

[TZANIDO777]

I ordered the rack stop from Turner last week for exactly this reason and to give me more clearance for brake duct hose.

[deesea]

Originally Posted by bNks334

7mm spacer at a minimum. My 255/40 RS3's are maybe 1mm off the strut with 17x9 ET45 (7mm spacer = ET38). 255 slicks would probably require a bit more spacing to keep the tire off the strut.

235 might fit, but why even bother with 9in rims if all you want to run is 235?

Primarily because I liked the style of the wheel.

Do you notice your 255/40's rub on the inside at full lock like what fe1rx is experiencing?

[bNks334]

Originally Posted by deesea

Primarily because I liked the style of the wheel.

Do you notice your 255/40's rub on the inside at full lock like what fe1rx is experiencing?

The Rs3's are a very square tire so they did grab the oil cooler shroud a bit when the were new. They might have touched the fender liner at full bump travel (potholes) while also under steering input.

255/40/17 does not rub the chassis at all with ET38. I also ran the same 18x8.5 arc-8 that felix has. I had 235/40/18 on those wheels too. I think they actually did rub the chassis in the same spot. Tire diameter might have something to do with it?

I don't spend any time at full lock. Not sure why you'd even be worried about some superficial grazing at full lock. The only time that would be a concern would be when parking which happens at low speeds anyway. I don't see any risk there.

[fe1rx]

Originally Posted by bNks334

The only time that would be a concern would be when parking which happens at low speeds anyway. I don't see any risk there.

Um, I think mine happened during some drifting sessions ...

[deesea]

Originally Posted by fe1rx

Um, I think mine happened during some drifting sessions ...

ding ding ding ding ding!

[Egghead652]

fe1rx, Can you provide the dimensions of the parts you made?

Turner doesn’t keep these in stock (2023 Estimated ship date).

Also, do you know if the E30, E36, or E46 versions would fit?

Thanks.

[fe1rx]

Originally Posted by Egghead652

fe1rx, Can you provide the dimensions of the parts you made?

The ID is 1.101" ±0.001" which made them a nice tight fit on the rack. No real need to tie the tolerance down quite that tight, but that is what I did. I preferred that they stayed where put, but if they were free to slide, I don't think that would really cause any problem.

The OD is 1.75".

Thickness I used was 10 mm (0.394").

[Egghead652]

Thanks.

[jplekid]

Originally Posted by fe1rx

The ID is 1.101" ±0.001" which made them a nice tight fit on the rack. No real need to tie the tolerance down quite that tight, but that is what I did. I preferred that they stayed where put, but if they were free to slide, I don't think that would really cause any problem.

The OD is 1.75".

Thickness I used was 10 mm (0.394").

Hi fe1rx, I'm new to the forum and unable to send PM (new user rule...).
I'm interested to talk about the steering stops you made.
Could you send me an email? jp_lekid@hotmail.com