suspension bottoming out

[Mexican]

Changed the shocks all the way around the other day since the suspension was too soft, after shock replacement i noticed no difference and car still bottoms out at bumps, does that mean my springs need replacement??

 

[mjlan]

Yes.

With the car sitting still, how far is the frame from the jounce bumpers? In the front they are on the out tower cover, and in the rear they are above the axle tube on the frame rail...

 

[Jeff73Mach1]

Yes-will make all the difference in the world as to how the car performs

 

[Hemikiller]

Definitely, change out the leafs for sure. In the front, the most common problem is that the suspension is just plain worn out, rarely do the coils fail.

 

[Carolina_Mountain_Mustangs]

I you have a shop that does leaf springs and yours are not really rusty you can have them re arched for less than new. They don't really wear out just over time loose some of the bow. When the cars were new they sat low in the rear. Even with comp. suspension. I think I put helper springs on my rear shocks about the second week after mine was delivered new.

David

 

[mustang7173]

Mexican,

Several articles and performance handling books that I have read have always referenced that you stay with the factory installed spring rates. This due to they provide the optimal ride per the installed equipment. They recommend to increase the front and rear sway bar size and or install a rear sway bar, depending on your factory installed handling equipment.

You can go to the Eaton Detroit Spring website and lookup your Grande to see what is recommended and determine what will best work for you.

https://www.eatondetroitspring.com/

Also, This book, Mustang Performance and Handling by Pet Sessler is a really good book to read up on the early mustangs.

http://www.amazon.com/Mustang-Performance-Handling-Guide-1964-1985/dp/0879381973

mustang7173

 

[Mexican]

Very interesting, will look at all the options and see what is better for my car, i even tought about installing adjustable shocks, i have them on my truck but have not checked out to see if they make them for my car

 

[Hemikiller]

My choice for best all around rear spring is the 71 429 spring. It has a reasonable rate and gives you a firmer ride without being harsh.

 

[mustang7173]

All,

After Hemikiller’s response, I had to go back to Eaton Detroit Springs and the Ford Motor Company Master Parts book to look up the specs for the 1971 Grande with 429 engine. Since the Grande is body code (65F) the 429 engine load rate before 10/19/1970 was 640 .lbs. After 10/19/1970, they dropped it to 615 .lbs load rate.

Now when you look up (65F) with 302 V8, with Competition option, before 10/19/1970, we have 590 .lbs load rate. After 10/19/1970 , the load rate increases to 615 .lbs load rate.

As Hemikiller pointed out, the Mustang Grande (65F) with the 429 engine, from 10-9-1970 , ML131 would be the ideal replacement leaf spring. I, myself, would order the ML131 and select the -1 to lower the body down for better handling.

I have added the FMC Master Parts Leaf Spring specs to help in determining your options.

Source: FMC Master Catalog, Copyright, May 1975 Section 50 – 5.4 pages 32 and 33

mustang7173 :bravo:

 

[Hemikiller]

The standard replacement number for the 429 spring is 42-547, you can use that at any spring shop or where I buy mine, Mustangs Unlimited. Had them in four Mustangs so far; 73 Grande', 2 x 71 sports roofs and now my current 71 Mach 1.

Personally, I would not recommend any drop in the rear leafs. The cars tend to sit a bit low in the rear from the factory and don't need any help, unless you are going to do some suspension work and lower the entire car.

If you decide to do front springs, the Moog 8534 is a good all around 302/351 spring. 430 lb/in rate. You might have to trim 1/2 a coil to get a non A/C 302 car down to a proper ride height.

 

[Mexican]

The standard replacement number for the 429 spring is 42-547, you can use that at any spring shop or where I buy mine, Mustangs Unlimited. Had them in four Mustangs so far; 73 Grandé', 2 x 71 sports roofs and now my current 71 Mach 1.

Personally, I would not recommend any drop in the rear leafs. The cars tend to sit a bit low in the rear from the factory and don't need any help, unless you are going to do some suspension work and lower the entire car.

If you decide to do front springs, the Moog 8534 is a good all around 302/351 spring. 430 lb/in rate. You might have to trim 1/2 a coil to get a non A/C 302 car down to a proper ride height.

Ecxelent posts!!

So, if i call Mustangs Unlimited and i tell them i want a pair of 42-547 shocks they will know what i am talking about? is it the same number for the rear?

 

[Hemikiller]

They should, but they are leaf springs...

http://www.mustangsunlimited.com/itemdy00.asp?T1=42547+01

I'd also recommend new front eye bolts, rear shackle kits w/bushings, and possibly the axle u-bolts. You never really know what you need until you start taking them apart. Start soaking down the front eye bolts with a penetrating oil now. They can come right out, or you may end up cutting the spring off them. I've been through the extremes with leaf spring replacements.

 

[TommyK]

I installed those leaf springs on Hemikiller's recommendation and have been very happy with them.

 

[Mexican]

They should, but they are leaf springs...

http://www.mustangsunlimited.com/itemdy00.asp?T1=42547+01

I'd also recommend new front eye bolts, rear shackle kits w/bushings, and possibly the axle u-bolts. You never really know what you need until you start taking them apart. Start soaking down the front eye bolts with a penetrating oil now. They can come right out, or you may end up cutting the spring off them. I've been through the extremes with leaf spring replacements.

Thanks for the link, i also have shocks on the back, what number would that be?

 

[Hemikiller]

They should, but they are leaf springs...

http://www.mustangsunlimited.com/itemdy00.asp?T1=42547+01

I'd also recommend new front eye bolts, rear shackle kits w/bushings, and possibly the axle u-bolts. You never really know what you need until you start taking them apart. Start soaking down the front eye bolts with a penetrating oil now. They can come right out, or you may end up cutting the spring off them. I've been through the extremes with leaf spring replacements.

Thanks for the link, i also have shocks on the back, what number would that be?

Ok, I don't follow. You already replaced the shocks and we were talking springs....

 

[will e]

Okay, I took the plunge and ordered the 42-547 springs from mustangsunlimited. They were cheaper than local, included free shipping and I know I will get something that works. I will take some before and after pics.