2 questions about rear coilover mounts [Archive]

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driftinblzr

10-23-2009, 10:47 AM

Hey All,

I'm thinking of switching to a 3-link from a leaf spring rear suspension for my Blazer.

First question) Which is the preferable way to mount the coilovers? Option A (bolts perpendicular to axle tube) or Option B (bolts parallel to axle tube)?

I assume on a street car Option A would allow more suspension travel with less bind during cornering compared to Option B.

Option A...
https://static1.pt-content.com/images/pt/2009/10/LowerShockMountStreet-1.jpg

Option B...
https://static1.pt-content.com/images/pt/2009/10/Shockmountdimension-1.jpg

Second question) Does anyone know or can get the dimension from the axle C/L to the C/L of the lower shock mounting bolt? I e-mailed Comp. Engineering and haven't received a response in the several days since I sent it.

Thanks for any input.

Later, Doug

The WidowMaker

10-23-2009, 06:59 PM

if the coil overs are angled, then both bolts must be perpendicular. if its straight, either will work.

if you do a crap load of searching, youll end up with #2. i found it a while ago, but dont remember where. they have their dimensions posted somewhere.

CRead01

10-23-2009, 07:44 PM

the nice thing about B is that the bolts are in double shear.

MCMLXIX

10-23-2009, 08:15 PM

https://static1.pt-content.com/images/noimg.gif

6227
ELIMINATOR II STRAIGHT SHOCK MOUNT
Price $ 89.00
For use with our Eliminator II chassis, this billet machined lower shock mount is offset to allow the top and bottom brackets to be in line and mount the shock vertical.

www.cachassisworks.com

gkring

10-23-2009, 08:45 PM

As far as the second question, use a plumb bob to mark the two centerlines on the floor, then measure the distance.

JRouche

10-23-2009, 09:53 PM

Very good question...

Ok, I went from the double shear to single shear.

Why?? Well packaging and suspension movement..

Double shear is best, ALWAYS. Some of the pin mounts that are in single shear are ok.

But I would look for an arrangement that has the bolt in a double shear AND parallel to the axle tube. That would be the best setup, if you can package that in there.. May have to make it.. So then you are in double shear for the bolt and also have sideways movement (pivot) for the lower coilover mount when the suspension moves.

And by the way, even though the second pic has the bolt in double shear its wrong!! See all the threads on the wrong side of the shear point, inside of the mount. Dont do that. Buy bolts with the correct grip length and if they have like three inches of threads hanging out trim the bolt. Cut those extra threads off. Buy your bolts for grip length first, then trim the extra threads off. Bolts in shear need to be in shear on the grip section, NOT a threaded section. Failure.

There isnt much additional cost for a longer bolt that has the correct grip length and trimming the extra threads off. Dont put a major suspension bolt in shear on the threaded section of the bolt. Bad voodoo there. Fifty cents more and some trimming of the bolt will get you years of life.

What I like is to have 1/32" of grip protruding from the outside of the mount. Then my thick USA made washers will take up the thread and allow the nut to seat before it hits the bottom of the threads.

Does that take some looking, for the correct bolts? Heck yeah!!!! I have looked high and low just for the correct grip length. And quality bolts. I have narrowed down my suppliers to three companies, and they all happen to be within a half mile of each other and five miles from me.

Fastenel, CAT and Grainger. All quality bolt suppliers. Grainger doesnt say it, but they sell PFC (Porteous Fastener Company) bolts, and fastenel sells high quality, made in the USA bolts. And CAT, well any guy from the farm industry knows CAT (catapillar) fasteners are top of the line.

Bolts have kinda become my interest while I was building the rear suspension. I did alot of research. The NAS or MS and various aircraft bolts. I called all around the country trying to track down the bolts I needed. 5/8" bolts in aircraft are far and few. And REALLY expensive. 90 bucks a bolt and I needed six of them. Aircraft bolts were outta the question for me.

So anyway. The bolts are critical. You prolly dont ever hear about a bolt failure, Its always something else. But with a lil searching online for the correct grip length it can give a lil piece of mind. I mean really, when you can put the correct bolt in shear wy wouldnt you. Specially when the cost of the bolt is minimal. JR

driftinblzr

10-24-2009, 06:56 AM

As far as the second question, use a plumb bob to mark the two centerlines on the floor, then measure the distance.

I'm still in the designing process so I don't have any parts yet to measure. I'm just trying to figure out that if I was to use Option B, would the coilovers be close enough to vertical, in side view, if I were to utilize the stock upper shock mount location.

Thanks JR for the good info about the bolts.

Later, Doug

gkring

10-24-2009, 08:17 AM

I'm still in the designing process so I don't have any parts yet to measure. I'm just trying to figure out that if I was to use Option B, would the coilovers be close enough to vertical, in side view, if I were to utilize the stock upper shock mount location.

Thanks JR for the good info about the bolts.

Later, Doug

You can still do the same thing. Plumb bob from the stock mount to the floor. The axle centerline should be easy as well. The difference between the two pints tells you how far the shock mount will have to be if you want it straight up and down. You should be very close to correct if the factory shocks were already in line.

The WidowMaker

10-24-2009, 11:33 AM

i think hes wondering if it will still be straight if he buys those mounts, which he currently doesnt have to measure. i may be reading it wrong though.

i used the ones that mcmlxix posted. my shocks are angled about 5 *.

driftinblzr

10-24-2009, 01:14 PM

i think hes wondering if it will still be straight if he buys those mounts, which he currently doesnt have to measure.

Exactly!! So can anyone grab a measurement?

Later, Doug

LowBuckX

10-25-2009, 07:58 AM

A 5/8 grade 8 or 9 in single shear is stronger than the sheet metal mount its bolted to. Double shear is strong but 5/8 bolts in single are plenty.

JRouche

10-25-2009, 06:00 PM

A 5/8 grade 8 or 9 in single shear is stronger than the sheet metal mount its bolted to. Double shear is strong but 5/8 bolts in single are plenty.

Good point... The stresses we are looking at dont come close to the failure point of a quality 5/8" bolt. And thats why I decided on using the 5/8" bolt in single shear on my car. And being able to torque the bolt down to a solid number, say 120 ft/lbs is even better. These quality bolts like to have some stretch on them. JR

driftinblzr

10-26-2009, 03:37 PM

Still looking for a dimension....anyone?

Later, Doug

MonzaRacer

10-27-2009, 01:17 AM

driftinblzr

10-27-2009, 03:54 AM

If your going to mod your rear suspension why not give Air Ride Technologies a call, They have a great parallel 4 link and you may even be able to use the 3 link S10 set up with mods.
Also I am not bigfan of full vertical coil overs on corner carving. some angle usually in the 10-15 percent ,in at top works best. check out ridetech.com or give a call to darren or pm darren@ridetech, honestly for driver/performance/handling the Air Ride is probably the bang for the buck made.
And yesI do have Air Ride on my truck and will be building a custom setup for my Monza and using Cool Ride for my Caprice.

I figured that I'll have less than $1500 in a full custom 3-link that should hopefully be close to 100% bolt-on. The Air Ride stuff is nice but way too much $$ for my budget and it would take a lot of modding to fit the Blazer. If I have to mod something that much to make it work, I might as well design my own system.

Later, Doug