Little clunks in steering - NOT the steering rack thread

[ChrisH]

Generally when I have seen someone report little clunks felt in the steering, a bunch of people will immediately reply saying it is the steering rack, with a few people saying to check the bolt/nut torques and bushings in the front suspension. I have had the same problem with little clunks that were slowly getting worse (and was dreading buying a steering rack), and it turns out it was loose bolts in the suspension, NOT the steering rack. So, I thought I would start a thread dedicated to tracking down little clunks felt through the steering that are NOT the steering rack so we have a place to collect such reports.

In my case, it was the bolts that hold down the bracket into which the upper end of the damper (shock absorber) is bolted. The bracket is secured by two bolts and nuts to the frame. There is one bracket for each side of the car, for a total of four bolts and nuts. The nuts have nylon inserts so that won't come off the bolt even if not torqued fully. However, the bracket is supposed to stay in place (no slipping), by its friction with the frame member. If the bolts are loose, it slides around, creating little clunks.

In my case, all four bolts were loose. I estimate they had less than 5 ft-lbs on them. The specification is 25 Nm (just over 18 ft-lbs). You can reach the lower bolt with a box end wrench (which is how I initially determined that at least the lower bolts were loose, and making me suspect the upper), but to tighten them all with a torque wrench, you need to remove the damper/spring, which is pretty easy to do (coil compressor is not needed). There are hidden nuts behind the piece to which the bracket is attached. You need to use a 13mm open end wrench to hold the nut still while tightening the bolt head with the torque wrench. I added a few ft-lbs (tightened to 20) just to add a little safety against the bracket slipping. The bolt is class 8.8. If this is a problem again, I will probably replace the bolts and nuts with class 10.9 and torque higher.

The frame member holes on one side did appear to be a little chewed up as if by the threads of the bolts, so I am guessing that it was that side that was causing the clunks. The bolts themselves showed no damage. By-the-way, the illustration in the Elise parts list only shows a single bolt holding down the bracket. There are actually two per bracket.

After tightening the bolts, the little clunks were gone!

I did check all other bolt and nut torques, and they were all good (except I didn't check the lower bushing clamp to frame bolt for the anti-sway bar, which I couldn't access; but, the upper clamp bolt seemed fine). Also, I never noticed any free play in the steering, and hence suspected and hoped something was simply loose.

The concern with these upper damper bracket bolts is that people checking the suspension bolt/nut torques may not be checking these because you have to take the damper off to properly access them. I really recommend to take the damper off and check these. It is easy.

I have another case I should be reporting soon about Pagid brake pads causing little clunks (and chattering), but I want to finish testing my fix for that one before reporting it.

If you have repaired any little steering clunks that weren't the steering rack, please report or link the post here.

[larez2]

nice find! how long did it take you tighten the bolts including the removal and reinstall of the damper/spring?

[CALtd]

A picture is worth while to add to this discussion.

[ChrisH]

Originally Posted by larez2

nice find! how long did it take you tighten the bolts including the removal and reinstall of the damper/spring?

Once I figured out that those bolts were the problem, it took less than an hour for the job, and that's being careful and slow.

[fpitas]

No clunks felt, but my front lower ball joints were barely tight, so be sure to check those too.

[Twerthi]

Can someone post pictures of both driver and passenger side with arrows pointing to the pieces in question? I'd like to get a good visual representation.

[catapult]

Intermediate u-joint (or something like that).

[ChrisH]

Originally Posted by Twerthi

Can someone post pictures of both driver and passenger side with arrows pointing to the pieces in question? I'd like to get a good visual representation.

Go back to post 3 in this thread for a graphic of the bracket that was loose.

[RoadDad]

First place, IMHO, to start checking for "little clunks in steering" is the wheel bolt torque.



No, I'm not kidding.

[CALtd]

I checked the bolts this afternoon and found that the passenger side lower bolt was stripped and would not tighten down. I went to the local auto zone and replaced all 4. Replacements are stronger as suggested by Chris and have flanged heads. So, shorter works without washers. The knurling bites into the aluminum and I added some blue locktite.

I am still not clear why I only had clunking once the car was hot, but I will go out for a drive this weekend and test it out. Attached shameless commercial for bolts used.

[CALtd]

Originally Posted by RoadDad

First place, IMHO, to start checking for "little clunks in steering" is the wheel bolt torque.



No, I'm not kidding.

I torque the wheels before and after each session, but to no avail, the clunk was always there at the end of a track day. By the time I got home 4 hours later, clunk was gone. Same when doing a 2 hour spirited drive; clunks on hot days and none when cool.

[plastique999]

I have a clunk as well on slow turns when I am turning sharply left or right. I was told this was my LSD- I have a kusco LSD. Anyone else have this issue?

[ChrisH]

After checking the torques on my suspension bolts, and tightening the obviously loose upper damper bracket-to-frame bolts, my handling definitely feels tighter now. My daily commute is a twisty road (Highland Valley Road in San Diego County), and I am pretty well calibrated on how the car handles and feels on that road. I have driven it multiple times since I tightened the bolts. The difference in handling may be objectively small (if there was a way to measure handling feel), but it is noticable. And, my handling clunks and clicks have not returned. I recommend you check those bolts even if you don't have clunks.

[ChrisH]

Originally Posted by CALtd

I checked the bolts this afternoon and found that the passenger side lower bolt was stripped and would not tighten down. I went to the local auto zone and replaced all 4. Replacements are stronger as suggested by Chris and have flanged heads. So, shorter works without washers. The knurling bites into the aluminum and I added some blue locktite.

I am still not clear why I only had clunking once the car was hot, but I will go out for a drive this weekend and test it out. Attached shameless commercial for bolts used.

For anyone who wants to upgrade their bolts, look at the first post in the engine mount bolt torque thread for a couple of links to the best torque charts for various bolt sizes I could find. (Some of the bolt torque sources on the internet didn't look right.)
Engine Mount Bolt Torques

So, for Class 10.9, M8 x 1.25 mm pitch (with upgraded nuts as well) as Craig used, the dry torque would be as follows
Dry Unplated: 34 Nm = 25.5 ft-lbs
Dry Zinc Plated: 37 Nm = 27.75 ft-lbs
Lubed with machine oil (unplated): 27.3 Nm = 20.2 ft-lbs

Many have said that if you use a thread locker compound (like LocTite), then you should use the lubed torque values. However, thread locker is not as good of a lubricant as machine oil (for which the lubed specification was made), so I can't really tell you which value is appropriate if you are using thread locker. However, even the lubed torque is greater than the torque for the original Class 8.8 bolts that Lotus used, so you can be confident that you will have much greater clamping force for the bracket to the frame than for the original bolts.

[CALtd]

Darn, I didn't know about increased torque settings with the new bolts. Now I am going to have to do it all over again. I used 20ft-lbs, the lowest setting on my torque wrench.

[RoadDad]

Originally Posted by ChrisH

For anyone who wants to upgrade their bolts, look at the first post in the engine mount bolt torque thread for a couple of links to the best torque charts for various bolt sizes I could find. (Some of the bolt torque sources on the internet didn't look right.)
Engine Mount Bolt Torques

So, for Grade 10.9, M8 x 1.25 mm pitch (with upgraded nuts as well) as Craig used, the dry torque would be as follows
Dry Unplated: 34 Nm = 25.5 ft-lbs
Dry Zinc Plated: 37 Nm = 27.75 ft-lbs
Lubed with machine oil (unplated): 27.3 Nm = 20.2 ft-lbs

Many have said that if you use a thread locker compound (like LocTite), then you should use the lubed torque values. However, thread locker is not as good of a lubricant as machine oil (for which the lubed specification was made), so I can't really tell you which value is appropriate if you are using thread locker. However, even the lubed torque is greater than the torque for the original grade 8.8 bolts that Lotus used, so you can be confident that you will have much greater clamping force for the bracket to the frame than for the original bolts.

Originally Posted by CALtd

Darn, I didn't know about increased torque settings with the new bolts. Now I am going to have to do it all over again. I used 20ft-lbs, the lowest setting on my torque wrench.

Although often incorrectly used synonymously, be careful when looking up the torque values for bolts as Grade and Class are not the same. Grade typically represents the SAE J429 designation and Class is the ISO R898 designation. (Then there are the ASTM A193, A307, A320, A449, A325, A354, A490, A194 and A563 classifications also which are either "Grade" or "Type" and a combination of letters and numbers like Grade B5, Grade A, Grade LC7, Type 1, Grade BB, Grade 1, Grade A, etc. ).

The bolts used by CALtd are Class 10.9 not "Grade" 10.9. For alloy steel these would have a proof load of 830 MPa, minimum yield strength of 940 MPa and a minimum tensile strength of 1040 MPa which is very close to a Grade 8 bolt (120,000 psi (load), 130,000 psi (yield) and 150,000 psi (tensile)).

Just don't get a Class 8.8 (85,000 (load), 92,000 (yield) and 120,000 (tensile)) confused with a Grade 8, 8.1, etc. .

[ChrisH]

Ah, thanks for pointing out the grade-class difference. I'll correct my posts.

[CALtd]

Goody, I don't have to take it all apart again to re-torque the new bolts.

Did a short drive this morning but it didn't get warm enough to tell if anything is different. Car felt the same as I remember it but I was not really pushing too hard. I need to have someone faster than me in front to follow lest I get lazy and too cautious.

[RoadDad]

Originally Posted by CALtd

Goody, I don't have to take it all apart again to re-torque the new bolts.

That's the exact confusion that I was hoping to avoid . Sorry if I made things worse.

The bolts are Class 8.8, not Grade 8, and your new ones are Class 10.9 so your torque values are different from what was previously there.

Even if the old bolt was Grade 8 with pretty close load, yield and tension values, the torque value for a Class 10.9 will be different.

You need to look up the torque value for the Class 10.9 M8 x 1.25 bolt (diameter and thread pitch).

[ChrisH]

Craig, the torque values I listed for the 10.9 bolts were for class, not grade. I was just being sloppy with my words. So, if you wanted to use your new upgraded bolts to their maximum rated clamping force, you would have to torque them a bit more.