Suspension Bolt Size

If your car has been using a bushing bolt larger than OEM, then the holes on all of your a arm mounting brackets would also need to have been enlarged to accommodate the larger bolt.

Without some corrective bushings to accommodate the smaller bolt in the enlarged mounting bracket holes, I see a problem with you returning to 0EM diameter bolts.

or am I missing something?

Larry

The bolts used before were probably 1/2” and the holes in the mounting brackets would have been enlarged accordingly. That now makes it impossible to use 12mm bolts. Perhaps the holes in the new bushings could be reamed out to 1/2”.

Larry, Unfortunately I think you are correct. I’ll give you a call tomorrow to see what the best option would be. I’m going to need a solution for front and back.

David, Agree. They appear to be 1/2”.

Thanks.

Shashi,

while my name is Larry and I am in California, I am not the Pantera vendor Larry Stock that it appears you think I am??

😉😉

Larry Finch

These would appear to be one solution to your dilemma. I found these with just two minutes of searching so you may find other sources and examples.

Larry

Thanks, Larry! Sorry about the confusion.

This might be a stupid question but is it possible the bolt hole of the a arm brackets can standardly accommodate the 1/2” bolt. It seems odd that someone would enlarge the holes to 1/2”, a lot of work to accommodate bushings. The bushings that I replaced appear to be the poly graphite with the hex inner sleeve which were available from at least Precision Performance. Thanks.

12mm = 0.472”

I think what Larry’s trying to point out is, 1/2” is less than 1/32” larger than 12mm. Enlarging the suspension mount holes to 1/2” is pretty easy. Also, you’ll find it’s easier and cheaper to find the appropriate hardware in 1/2”, than it is in 12mm.

Why are you replacing Dennis’ bushings?

Thanks David, I should’ve been more clear. I don’t think the 12 mm holes had enough OEM slop to allow the larger bolts without them being enlarged. A simple ten second task with a half inch drill bit chucked into a cordless drill;  and a lazy and ill advised action that will forever plague and perplex future owners until it is returned to OEM  dimensions.

as for the bushings being from Dennis Quella I agree (not the now-defunct Precision Proformance run by the late Bob Byars). Dennis is the only vendor I am aware of that has the hexagonal center section.

Larry

Thanks, guys. I think I just had to go through the stages of grief to suck it up. I think David is correct in that I just need to opt for bushings with the 1/2” bolt. It probably isn’t the end of the world. I might be able to pick some up from Energy Suspension. I will measure it out tomorrow.

David, to your question about why in am changing the graphite bushings; somewhere in the car’s past only  three wheels were updated to the graphite bushings. For some odd reason the passenger rear was something else, and deteriorated. The whole rear suspension is being gone through so I thought a new set of poly bushings would be easy.

I think it is going to prove difficult, if not impossible, to find a bushing with an SAE inside diameter but a metric outside diameter.

IMHO, The right thing as the current caretaker of the car is to take the steps necessary to correct the mutilation done by a previous owner.

Larry

Larry, I certainly don't consider enlarging the suspension mount bolt holes to 1/2" "mutilation", if it was done as part of an overall improvement. Obviously, Dennis Q.'s bushings do indeed have a 1/2" ID and metric OD. I can see Dennis doing this because he's always complaining about the Pantera's junk metric hardware.

FYI, Dennis advises changing the steering arm to spindle mounting bolts from M10 to AN7/16". Apparently, there's a problem with the M10 bolts breaking!!! As a long time Pantera owner, that's news to me! On the other hand, there's likely no one who's seen more Panteras than Dennis, so if he says it's a problem...

Shashi27, there are two obvious, easy solutions to your bushing problem. The first being, just buy a new set of bushings from Dennis; the same ones as on the car now. The second being, buy whatever bushings you want and ream the metric center hole out to 1/2". As the amount of material being removed is so minimal, I can't see it causing a problem.

David, have you confirmed that Dennis’ bushings are actually supplied from him with an inside diameter of 1/2 an inch?

Larry

No, I have not. If they come with a 12mm ID, would someone go the effort of enlarging the hole to 1/2" and why???

Looking at the poly bushings, I don’t think I need to ream the bushings, I think I need to have the sleeves cut to a larger inner diameter, a thinner sleeve.

BTW, “the other Larry” said the chassis holes are 12.3mm (.480”). So there is a little play already there. That still doesn’t account for my car accepting the 1/2” bolts though.

I also left a van with Dennis to see if he can let me know his thoughts.

Will keep you posted. Thanks

I was able to get in touch with Dennis. He doesn’t make the bushings anymore but did say they were 12M.

I also connected with Larry Stock who is working on my uprights and he didn’t think the larger size hole was significant to make much of an issue as the the bolts are cranked down pretty tight on the chassis. For now I’ll use the 12M bolts, then get it properly welded when the car goes in for paint.

Thanks.  

So you will be using the new bushings that have a 12 mm ID and the OEM-correct 12 mm bolts.

but using those 12 mm bolts and 1/2 inch bracket holes will, as you know, leave the potential for movement. I do not believe the forces at work in the suspension of a 3000 pound car can be overcome by tightening the 12 mm mounting bolts.

I believe you could use the adapter bushings I posted earlier without actually welding them in place. For that action I believe tightening the bolts would certainly be sufficient, and safer than allowing your suspension to have 16 points of potential movement  

I would certainly advise welding them in place at the earliest convenient moment.

Larry

Thanks. That’s a great idea. I’ll also see if I can get a mobile welder to come and do it while I have the suspension out.

Note that OEM 12mm bolts were the metric equivalent of Gr-5. Nowadays, 12mm bolts can be had in Gr-8 if you're concerned about strength.

It is critical that you weld the step washers to the suspension mounting tabs as you’ll be relying on the washers for strength. The inserts that reduce the ID of the holes will only be 0.013”, which is paper thin. Any movement and they’re gone. Have you considered just welding up the holes and re-drilling them to 12mm? Welding on those tabs won’t be easy as some of them aren’t too accessible. Even cleaning them up for welding won’t be easy. I still think the easiest way to solve your problem is to enlarge the holes in the new bushings to 1/2”.

Alrighty. Update time.

I took the bushing sleeves (poly so they pop out) to my local machine shop. He is going to ream out the inside diameter from 12mm to 1/2”. I also ordered some aircraft bolts with grips long enough to pass from hole to hole, which I think provides the appropriate rigidity.