I've read that this size rim will fit with stock trailing arms and that the stock rear spring will sit in the rim at normal ride height (29.5"). My question is if I go with 10" bolts and drop it 2.5" to 27", will this then move the spring back down to the rim? I have a stock composite spring and was wondering if it can/should be cut back if I go this route.

 

I can give you some very good advice on this. Please don't buy wheels until you are sure the backspace will work. A guy from a custom wheel manufacturer swore up and down that I could go 5" or more (can't remember the exact number) on the rear. If I had followed his advice, I would have thrown away $1350 for the 2 rears (or I would have had to change the spring). I ordered a Percy's WheelRite tool and found that my max backspace is 4.5". I have the higher rate springs from Van Steel. The springs are definitely the limiting factor on my setup. I have a set of 10" bolts and may use them if I can't get the ride height correct with the 8" bolts.

I think there are too many variables, and would rather spend the $90 on the wheelrite and be sure. http://store.summitracing.com/partde...5&autoview=sku

I ended up ordering 18x10 4.5 BS Torq Thrust IIs for the rear and 17x8 4.5"bs in the front. Here are some pics.
http://web.mac.com/clsjohnson/iWeb/7...els_Tires.html

In these pics, the car is riding high and the spring isn't extended like it will be under acceleration. When I measured with the tool, I had the jack under the one shock mount so the entire rear's weight was on one side of the spring.





EDIT: This pic will show that 10" wheels and 4.5" bs is going to stick out an inch or two, and will look better with flares...


In this pic, I don't have the rear trim on, I haven't installed the flares yet, the height isn't set yet, the motor isn't in the car, so it doesn't look like it will

 

I have 18x10s with 5.5" backspacing. I also have offset trailing arms, 10" bolts and my rear spring is 1.5" shorter than stock. See the pic below for where my spring sets in relationship to the wheel/tires. I also had to remove the swaybar as the wheel/tire rubbed on hard turns. Rod

 

Would the shorter spring be necessary if you only had an 8 inch bolt? This is the set up I would like to do, but I don’t want to get another spring. I have the offset trailing arm already so no problem there.

EDIT>>> It looks like the spring would tuck inside the wheel if the bolt was shorter.

 

I am running a 18X10 with a 5.5 backspace and stock trailing arms. Here is a shot of my dual mount spring. I can't remember if this is the 1 inch shorter both sides or the 1/2 shorter both sides. It is with 8 inch bolts. I am now running the 1/2 shorter spring. The 1 inch shorter was the wrong spring rate so I exchanged it for a harder spring and I only wanted it 1/2 inch shorter.

 

The shorter spring is the key. I have 15 X 10" Convo Pros with 5" backspace on my '74. I have a composite spring that is 1.5" shorter than stock. I have about 3/8" of an inch clearance between the rim and the spring. I have read that you can get 5.5" backspace if you go with 18" rims.

If you don't want to buy a new spring, there was a post on the forum a year or so ago with instructions for redrilling the hole in an existing spring and then cutting it yourself - I don't recall who posted it, but you should be able to do a search on it.

 

Thanks for the info...I remember that post now that you mention it. I’ll see if I can find it. I really want to go with the 10” wheel as long as I can get it all to tuck under the fender. I guess if I need to I could sell the spring on there and get the shorter one.

 

Could you post the link if you find it? Thanks

 

Thanks for the pics. Very . It looks like shorter spring is needed for the 10" bolts. I've been told that offset trailing arms are not needed and issue is really the frame before the t/a's. I also e-mailed VanSteel and Dan cautioned me that I could bind the half shafts if they are not kept on a slight downward angle when lowering (that's something I didn't think of) and to keep the bolt higher than the rim in case of a flat.

Not sure if this the one but it gives the process of cutting a rear spring.

http://forums.corvetteforum.com/show....php?t=1416946

 

I just read all the stuff in here and i have a fitment question.Ihave a 70 bb and would like to use 17x8.5 w/4.5backspace and 255/70r17 on rear----17x8 w4.5backspace and 255/45r17 on front WHAT SURPRISES AM I IN FOR ????????????

 

I don't see why that wouldn't work, some C3's came stock with 255's. A 255 on a 15" rim(stock) would actually be wider on the sidewall than the sidewall of a 255 on a 17" rim.

 

255/70 rear tire is very very very very tall (did I mention it was tall) I think a 255/45 front and a 255/50 - 17 rear would work better.
The 4.5" backspace on the rear shouldnt be a problem.
On the front, just check how close the tie rod is to your current 4" backspace wheels, some guys have issues with it bieng close.

Nick

 

255/70 rear tire is very very very very tall

Didn't catch that Nick, it might be a typo...that is really tall

 

So If I were to upgrade to the VBP rear dual mount composite mono spring that eliminates the rear sway would I then be able to alleviate running into this problem?

 

we're talkinga bout the width of the spring from one side of the car to the other right?

I dont know this older suspension tech, so please bare with me and the stupid questions I'm trying to understand.

I want to do 10" bolts, and I was planning on on doing the VBP dual mount composite monospring... which as far as I know only come in one size for an 81... should I be asking for a shorter spring?

 

Yes it is the meaurement from side to side. I have 8 inch bolts on my setup as you have pictured and they are up a little, probably only using 7 inches of the bolt. The 10 inch bolts would be to long for me. My ride height is right at 27 .5 inches, and the half shaft are level to the ground.

You can custom order any width spring from VB you want. They will make it for you. The spring rate is also variable, I asked for a little stiffer spring rate as the first one even set on the stiffest setting was to soft.