Ground Clearance
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
Ground Clearance
Greetings All,
I'm thinking my '70 convertible BB sits too low in the rear. I measured the clearance from the exhaust pipes to the ground and it's only 2.25 inches. All my research is pointing towards the leaf spring, but I thought I would see what you all thought as well. Also, the tires on the car are P235/60R15.
I'm thinking my '70 convertible BB sits too low in the rear. I measured the clearance from the exhaust pipes to the ground and it's only 2.25 inches. All my research is pointing towards the leaf spring, but I thought I would see what you all thought as well. Also, the tires on the car are P235/60R15.
Team Owner
Joined: Sep 2006
Posts: 31,172
Likes: 4,250
From: Westminster Maryland
Hi ZRX,
It DOES look like the pipes are close to the ground.
Originally the bb pipes were 'flattened' in the area where they pass under the rear spring and strut rod bracket. I can't quite see if those are or not?
You might begin by checking the 'ride height' to see if that's contributing to the clearance situation.
The dimension from the ground to the center ion the wheel arches was typically about 28".
Your 235/60 tires are bit shorter than the original tires which will drop the car down a little.
Lot's of things can affect that dimension but it'll give you a start.
Regards,
Alan
It DOES look like the pipes are close to the ground.
Originally the bb pipes were 'flattened' in the area where they pass under the rear spring and strut rod bracket. I can't quite see if those are or not?
You might begin by checking the 'ride height' to see if that's contributing to the clearance situation.
The dimension from the ground to the center ion the wheel arches was typically about 28".
Your 235/60 tires are bit shorter than the original tires which will drop the car down a little.
Lot's of things can affect that dimension but it'll give you a start.
Regards,
Alan
Last edited by Alan 71; Feb 26, 2018 at 05:28 PM.
Team Owner
Joined: Sep 2002
Posts: 38,289
Likes: 2,065
From: California
Damn you got me beat, and I am running an eight quart oil pan, and side exhaust hookers with the 4" collectors. I have to watch dragging the headers over the crest of driveways. The oil pan hates speeds bumps. But I actually was running old 1950 curb feelers out on the front spoiler, and if the whiskers scraped, then I knew to stop and back up and try a different plan. I do carry blocks of wood in the storage compartments, just in case I have to get two of the cars home!
Last edited by TCracingCA; Feb 26, 2018 at 05:32 PM.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,753
From: Charlotte NC
YES....I would say that it is very low and there is an issue.
A lot of it also depends on what the photo does not show and that is how close are those two pipes to the plate that holds the rear spring to the differential cover.
DUB
A lot of it also depends on what the photo does not show and that is how close are those two pipes to the plate that holds the rear spring to the differential cover.
DUB
Drifting
Joined: Aug 2015
Posts: 1,939
Likes: 477
From: NSW, Australia
C3 of Year Finalist (track prepared) 2019
235/60R15 will lower the car 0.5-1" compared to stock too (~0.5" compared to 255/60R15, almost 1" compared to 225/70R15).
Last edited by Metalhead140; Feb 26, 2018 at 09:10 PM.
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
Hi ZRX,
It DOES look like the pipes are close to the ground.
Originally the bb pipes were 'flattened' in the area where they pass under the rear spring and strut rod bracket. I can't quite see if those are or not?
You might begin by checking the 'ride height' to see if that's contributing to the clearance situation.
The dimension from the ground to the center ion the wheel arches was typically about 28".
Your 235/60 tires are bit shorter than the original tires which will drop the car down a little.
Lot's of things can affect that dimension but it'll give you a start.
Regards,
Alan
It DOES look like the pipes are close to the ground.
Originally the bb pipes were 'flattened' in the area where they pass under the rear spring and strut rod bracket. I can't quite see if those are or not?
You might begin by checking the 'ride height' to see if that's contributing to the clearance situation.
The dimension from the ground to the center ion the wheel arches was typically about 28".
Your 235/60 tires are bit shorter than the original tires which will drop the car down a little.
Lot's of things can affect that dimension but it'll give you a start.
Regards,
Alan
Last edited by ZRXGreen; Feb 26, 2018 at 11:29 PM. Reason: Added info
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
DUB, I ordered some race ramps that should help me see what's going on back there. When I get them, I'll snap some pics of the area and post them here.
Team Owner
Joined: Sep 2006
Posts: 31,172
Likes: 4,250
From: Westminster Maryland
Hi ZRX,
Those numbers indicate that the car is sitting a bit low.
While the tires that are on the car are contributing to that, it could be various other things too.
So you'll need to determine if it's the exhaust system that isn't tucked up under the chassis properly, or if it's the suspension that's allowing to sit low, or is it a COMBINATION of those 2 things?
Some photos of the rear suspension will begin to answer that question.
Normally when the car is sitting on the ground the half shafts should be parallel or close to parallel with the ground and almost all the arch should be removed from the rear spring.
A couple of photos?
Regards,
Alan
Here's a car showing:
The FLATTENED exhaust pipe tucked tight up under the rear spring.
The rear spring with almost all the arch removed by the weight of the car.
The half-shafts running almost parallel with the road surface.
Those numbers indicate that the car is sitting a bit low.
While the tires that are on the car are contributing to that, it could be various other things too.
So you'll need to determine if it's the exhaust system that isn't tucked up under the chassis properly, or if it's the suspension that's allowing to sit low, or is it a COMBINATION of those 2 things?
Some photos of the rear suspension will begin to answer that question.
Normally when the car is sitting on the ground the half shafts should be parallel or close to parallel with the ground and almost all the arch should be removed from the rear spring.
A couple of photos?
Regards,
Alan
Here's a car showing:
The FLATTENED exhaust pipe tucked tight up under the rear spring.
The rear spring with almost all the arch removed by the weight of the car.
The half-shafts running almost parallel with the road surface.
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Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
Hi ZRX,
Those numbers indicate that the car is sitting a bit low.
While the tires that are on the car are contributing to that, it could be various other things too.
So you'll need to determine if it's the exhaust system that isn't tucked up under the chassis properly, or if it's the suspension that's allowing to sit low, or is it a COMBINATION of those 2 things?
Some photos of the rear suspension will begin to answer that question.
Normally when the car is sitting on the ground the half shafts should be parallel or close to parallel with the ground and almost all the arch should be removed from the rear spring.
A couple of photos?
Regards,
Alan
Here's a car showing:
The FLATTENED exhaust pipe tucked tight up under the rear spring.
The rear spring with almost all the arch removed by the weight of the car.
The half-shafts running almost parallel with the road surface.
Those numbers indicate that the car is sitting a bit low.
While the tires that are on the car are contributing to that, it could be various other things too.
So you'll need to determine if it's the exhaust system that isn't tucked up under the chassis properly, or if it's the suspension that's allowing to sit low, or is it a COMBINATION of those 2 things?
Some photos of the rear suspension will begin to answer that question.
Normally when the car is sitting on the ground the half shafts should be parallel or close to parallel with the ground and almost all the arch should be removed from the rear spring.
A couple of photos?
Regards,
Alan
Here's a car showing:
The FLATTENED exhaust pipe tucked tight up under the rear spring.
The rear spring with almost all the arch removed by the weight of the car.
The half-shafts running almost parallel with the road surface.
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
OCB, I've owned the car for about 2 weeks now. It was like that when I bought it, but because it was on a lift when I first looked at it, I didn't have the ground under it as a reference to notice the clearance. I don't believe the car was ever lowered.
Race Director
Joined: Mar 2016
Posts: 14,305
Likes: 8,110
From: Napa Valley California
If you can crawl under the rear and take some photos of the rear spring, spring bolts, half shafts and so on, it would truly help.
You should be able to get under the rear end far enough to get these photos without lifting the car.
Take a few around the car to show the stance so we can see that as well.
Last edited by OldCarBum; Feb 27, 2018 at 07:19 PM.
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
Congrats on your new corvette and welcome to the forum.
If you can crawl under the rear and take some photos of the rear spring, spring bolts, half shafts and so on, it would truly help.
You should be able to get under the rear end far enough to get these photos without lifting the car.
Take a few around the car to show the stance so we can see that as well.
If you can crawl under the rear and take some photos of the rear spring, spring bolts, half shafts and so on, it would truly help.
You should be able to get under the rear end far enough to get these photos without lifting the car.
Take a few around the car to show the stance so we can see that as well.
I posted a bunch of pics of the car in this thread here, which might give you a better overall picture of the stance. https://www.corvetteforum.com/forums...-the-club.html
Last edited by ZRXGreen; Feb 27, 2018 at 07:51 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Is there any reason OP can't get shorter spring bolts to raise the car in back? At least as an interim til he decides whether to do the rear spring? Those squashed lower bushings may be worth half an inch right off the bat.
Last edited by derekderek; Feb 27, 2018 at 08:41 PM.
Instructor
Joined: Sep 2011
Posts: 145
Likes: 22
From: San Francisco CA
Have you checked the tire date code on your new machine-often these hobby cars come with tires that look good but are aged out. If they are due for replacement that might be your first step.
Thread Starter
Racer
Joined: Dec 2017
Posts: 355
Likes: 46
From: Chicago Suburbs Illinois
Thank you. Funny you mention that--About a week ago, I scoured the tire but couldn't find any DOT number on the outside. I figure it must be on the inside of the tire, but again, since I can't really get under the car, I can't see. As soon as I get my ramps I'm going to check that as well.
Race Director
Joined: Mar 2016
Posts: 14,305
Likes: 8,110
From: Napa Valley California
Beautiful car, it looks to be in great condition.
Do the measurements Alan suggested and see what you get compared to OEM specs.
In the photos, it does appear to be lowered some.
I'm not sure how long the OEM spring bolts were for your year but on my 73 BB I believe they are 6.5 inches. Many will swap out the OEM bolts with 8 inch to lower the rear end.
Once you get your ramps take photos and measure the spring bolts.
You can always call the prior owner and ask him if he lowered the car, and if so, How.
Keep us posted.
Do the measurements Alan suggested and see what you get compared to OEM specs.
In the photos, it does appear to be lowered some.
I'm not sure how long the OEM spring bolts were for your year but on my 73 BB I believe they are 6.5 inches. Many will swap out the OEM bolts with 8 inch to lower the rear end.
Once you get your ramps take photos and measure the spring bolts.
You can always call the prior owner and ask him if he lowered the car, and if so, How.
Keep us posted.
Team Owner
Joined: Sep 2006
Posts: 31,172
Likes: 4,250
From: Westminster Maryland
Hi ZRX,
Yes.
All 68-72 cars left St.Louis with F70-15 tires on them.
The F70 tire was just shy of 27" tall.
The "P" & "R" Trim Height dimensions were just a hair below 28"
Regards,
Alan
These are F70 tires.
The ride height on this car is about 1/2" low in front (P) and about 1/2" high in the rear (R).
Yes.
All 68-72 cars left St.Louis with F70-15 tires on them.
The F70 tire was just shy of 27" tall.
The "P" & "R" Trim Height dimensions were just a hair below 28"
Regards,
Alan
These are F70 tires.
The ride height on this car is about 1/2" low in front (P) and about 1/2" high in the rear (R).
Last edited by Alan 71; Feb 28, 2018 at 12:58 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
I looked at one of the really pretty expensive restored car ads today and that new bushing under the bolt is a good over half an inch thick when it's compressed. The original one is squash down to where the metal plates almost touching. Has that spring ages it'll drop a little. Shorter spring bolts in new bushings will get that back end up where it belongs quickly inexpensively.