[wnazare]

I remember seeing a "minimal offset" kit either @ Speedwaymotors or CPP which I was considering using when I get to that point (hopefully this winter). I think it was less than a 1/4" on each side.

 

[roger1]

Anybody using this kit from CPP?
http://www.classicperform.com/Store/1955_1970_Fullsize_Cars/5557CBKD.htm

It only moves the wheels out 1/8" on each side. It doesn't state what size the rotors are. Anyone know that?

I would like to use 4.25 BS 15X7s with 225s and wonder if I could get away with that with this kit. The calculator says no, but just barely.

 

[bob p]

I don't know the rotor type, sorry. Its always been pretty difficult to get that information out of some vendors -- they view it as proprietary information, and I view that as kind of a joke. If you call CPP they should tell you something, and whatever they tell you will give you a lot of information about where to shop. At the time of purchase I'd want to know exactly what kind of replacement parts I'd be needing in the future, so that I know ahead of time whether I'm going to be locked into a single supplier for replacement parts. Custom replacement parts or overpriced generic replacement parts could make turn an inexpensive kit into a very expensive one over time, and IMO that's as good a reason as any to consider other kits. Good luck.

 

[roger1]

I don't know the rotor type, sorry. Its always been pretty difficult to get that information out of some vendors -- they view it as proprietary information, and I view that as kind of a joke. If you call CPP they should tell you something, and whatever they tell you will give you a lot of information about where to shop. At the time of purchase I'd want to know exactly what kind of replacement parts I'd be needing in the future, so that I know ahead of time whether I'm going to be locked into a single supplier for replacement parts. Custom replacement parts or overpriced generic replacement parts could make turn an inexpensive kit into a very expensive one over time, and IMO that's as good a reason as any to consider other kits. Good luck.

Just got off the phone with Aaron at CPP. Seemed knowledgeable about the product and willing to give me a straight answer on all my questions.

The kit I provided a link to that only moves the wheels out 1/8" per side has 10.5" rotors. The are OEM on the 79-81 Malibu. The calipers are OEM units for 82-92 S10 pickups. The spindles are cast steel with stamped brackets.

They also have a 12" rotor kit that uses a cast steel spindle with a integral bracket. These use 70 Chevelle rotors and 90's Camaro calipers. (I hope I didn't get that reversed in my notes.) The 12" kit is a $100 upgrade and moves the wheels out 3/8" per side.

I am interested in their 10.5" kit. Only one eighth per side is pretty good and you get a lot for the money with this kit. If I don't go this route, the only other consideration at this point for me is the TPP kit that moves the wheels in 1/4" per side. The TPP kit sure would make it more flexible for me on tire and wheel choices but is quite a bit more expensive. The TPP kit also uses an expensive replacement rotor.

Thoughts?

 

[BigBoyzToyz]

Anybody using this kit from CPP?
http://www.classicperform.com/Store/1955_1970_Fullsize_Cars/5557CBKD.htm

It only moves the wheels out 1/8" on each side. It doesn't state what size the rotors are. Anyone know that?

I would like to use 4.25 BS 15X7s with 225s and wonder if I could get away with that with this kit. The calculator says no, but just barely.

That kit moves out 3/8" to 1/2" each side, that's the Mcgaughy style spindle with 10.5" rotors. It is a bear to align without offset upper cross shafts also.

 

[roger1]

That kit moves out 3/8" to 1/2" each side, that's the Mcgaughy style spindle with 10.5" rotors. It is a bear to align without offset upper cross shafts also.

Wow, really, are they that untrustworthy? I even asked Aaron if the 1/8" was accurate and he said yes. If what you say is true about 3/8" to 1/2", they are out for me. I was figuring on getting the offset upper cross shafts anyway, so that part isn't an issue for me.

Toyz, do you think the TCI kit is quality? I could go with 15X8 wheels and 225s with that kit and have the same size wheel all the way around the car. It's really not that much more money if TCI kit is a good one.

 

[bob p]

I'm not sure that an 80 Malibu rotor will only move the wheel mounting surface out only 1/8" per side. There seem to be some mixed opinions on this. I've heard people say 1/8", but people that I trust here say 3/8". I used the 3/8" number when planning my upgrade just to be on the safe side.

Like BBT said, the consensus seems to be that an 80 Malibu rotor would move it out about 3/8" per side or 3/4" total; that number is attributable to the rotor's hat height, and AFAIK that number is true when the rotor sits on a Heidt spindle. I dunno about a McG spindle.

According to theTriFive drop spindle table , the McG spindle increases track by 1". Wow. Can that be right?

Even with only 3/8" outward displacement on a Heidt's spindle, its really tough to fit a 225 tire up front. The wheel backspace will be critical and fitment could be close. If the McG spindle is really 1", that could really restrict your wheel/tire options. It would be interesting to know if that 1" measurement is right for the McG spindle, and if the CPP spindle is an accurate knockoff (same dimensions/geometry).

Because of the potential for alignment problems, I spent more money and built my kit around the Heidt's drop spindle. I wanted a setup that had as little effect as possible on my steering geometry and it seemed to be the way to go.

There are many factors to consider, which can make things confusing. Sometimes its better to buy a more expensive kit, as they're cheaper in the long run. Especially if they don't muck up your alignment/steering and require to spend more time and money to fix them.

 

[BigBoyzToyz]

Nothing wrong with up to 1/2" per side for me. I just don't like that style of spindle. It causes steering problems also. I thought CPP had a new style 55/57 2" drop spindle that resembles a stock spindle?(kind of a Heidt's copy). Otherwise the heidt's style is much better.
I would suggest not using 8" wide wheels up front, save yourself lots of grief.
I usually use 7" with 3 3/4" to 4 1/4' backspace without problems on most any kit.
If CPP told me that toady was Friday I would have to go double check my calender!

As far as the TCI kit, I have never seen one. I would be cautious of any kit that uses a non-OEM rotor, in other words you are married to their pricing, not good.

 

[roger1]

OK. Just got off the phone with Jason at TCI. He said their drop spindle kit INCREASES the tracking width 1/4" per side and that the web page is wrong. I told him that they should get that corrected. And, btw, their caliper is an '80s Camaro OEM and their rotor is a modifed Chevelle and has a replacement cost of $104.

Well, I am kind of back to square one now. I would like to be able get 4.25" BS 15X7s with 225s on my '55 with no rubbing. I guess I could go with 215s if I had to.

Bob, will your setup do that? If so, what rotors do you use and are you using stock control arms?

Toyz, what do you think is the best way to go to accomplish the wheel and tire size I want?

 

[roger1]

Nothing wrong with up to 1/2" per side for me. I just don't like that style of spindle. It causes steering problems also. I thought CPP had a new style 55/57 2" drop spindle that resembles a stock spindle?(kind of a Heidt's copy). Otherwise the heidt's style is much better.

Are you assuming their online photo is accurate? It may not be.

I would suggest not using 8" wide wheels up front, save yourself lots of grief.
I usually use 7" with 3 3/4" to 4 1/4' backspace without problems on most any kit.

OK, I'll forget the 8s. But it seems like 7" wheels with that backspace is over the 68 number that the calculator suggests. I know you don't put a lot of faith in that calulator, but wow, that wheel combo you suggest when you go 1/2" per side wider puts you way, way over.

 

[tjsdelivery]

I used the zero offset kit from mgchevyparts on ebay (he's from Cal.) It fit great and was straight forward. I have H-70-15 tires with 3 3/4 backspace and it never rubbed on the fenders before the swap, but just a little on the frame. With the new kit, I have the same. This uses your stock spindle. All steering hooked back up exactly where it came off.

 

[bob p]

Well, I am kind of back to square one now. I would like to be able get 4.25" BS 15X7s with 225s on my '55 with no rubbing. I guess I could go with 215s if I had to.

Bob, will your setup do that? If so, what rotors do you use and are you using stock control arms?

I want to give you the most accurate answer possible, so I'm going to list my supplier part numbers:

Control arms: stock
Spindles: Heidt's 2" drop, with "early" brackets
Calipers: Raybestos RC4039 / RC4040 (69-72 Chevelle, big piston, loaded with pads)
Rotors: Raybestos 5038R (SAE spec, 79-81 Malibu, 10.5")
Wheels: see below

All of this wheel width and offset business gets confusing since backspace numbers change every time that you change wheel width. This means that if you think in terms of backspace, you have to constantly juggle lots of numbers in your head as you compare different wheel widths. It was driving me nuts.

To get away from that, I've started to think about my wheels in terms of offset rather than backspace. That way whenever I think about a 5" wheel, a 6" wheel, a 7" wheel or an 8" wheel, all that I have to remember is the proper offset number that's needed to keep the wheel centered. Once I realized that the "common denominator" for me was a 12mm positive (outward) offset, that made thinking about these things a lot simpler. I keep the 12mm number in my head and I use the chart to look up the equivalent backspace numbers, which I keep forgetting.

12mm offset on a 7" wheel is equivalent to 4.5" backspace.

Here's the chart:

more to follow...

 

[bob p]

When I ran the numbers on the calculator, it told me that if I wanted to run a 7" diameter wheel, then to fit a 225 tire I needed a backspace of 4.5". That's equivalent to a 12mm offset, and that's how I got the 12mm offset number.

Even though the wheel and tire would fit in the well well my problem was that the consensus of opinion seemed to be that there is no 14" wheel with a 4.5" BS that would clear my Early Chevelle large piston disc caliper. That meant that 14x7 @ 4.5 with a 225 tire was a no-go for me. My only options were to decrease the backspace, which would push the wheel out and risk rubbing, or go to a narrower tire.

I wasn't particularly interested in a narrower tire. Looking at the brake system I was designing, there was going to be plenty of hydraulic pressure at the calipers, and the rubber/road interface (not my foot, not the MC, not the caliper pistons) was going to be the weakest link in my disc brake setup. So I wanted to try to optimize the contact patch. Unfortunately, compromise becomes a necessary evil. To get the best braking, you need a fatter tire. To get a 225 tire centered you need a lot of backspace, and that backspace won't clear the calipers on 14" wheels. To run a 225 tire without rubbing I think you have to take the risk of rubbing with 14" disc brake wheels that have less backspace. It looked like the bottom line was that with 14" wheels I was going to have to go with narrower tires and accept inferior braking. (i know, its hairsplitting)

It was frustrating. Every time that I turned around I kept getting knocked back to square one. Eventually I became so frustrated that I thought about throwing in the towel on the 14" hubcaps / OEM look for my otherwise 100% original looking wagon and just buying a set of TT2.

In theory, a 15x7 @ 4.5" BS should clear a "small" 10.5" disk brake setup like the Early/Late GM A-body setups, and it would center a 225 tire in the sweet spot. So I looked for a 15x7 TT2 with 12mm offset. I couldn't source them either. Every turn led to more frustration. It was like I kept pulling that Monopoly card that said, "Go to Jail. Go directly to Jail. Do not pass Go. Do not collect $200."

Drat. Even though 15" gives you LOTS more tire options than 14", I still couldn't find a set of wheels that I liked that would fit my car.

Now I was thinking that now that I'm out of 14" wheels, what's the point of confining myself to 15"? 16" gives you LOTS more tire/wheel options, so I began looking for a set of 16x7 TT2 with a 12mm offset to mount a 225 tire. I had no luck sourcing that wheel either.

I never found a 15x7" wheel with a 12mm offset that I liked, so to answer your question: I've never tried mounting one. In theory the fit would be fine on my setup. I just can't say that I've actually done it.

still more...

 

[roger1]

I used the zero offset kit from mgchevyparts on ebay (he's from Cal.) It fit great and was straight forward. I have H-70-15 tires with 3 3/4 backspace and it never rubbed on the fenders before the swap, but just a little on the frame. With the new kit, I have the same. This uses your stock spindle. All steering hooked back up exactly where it came off.

That's an interesting kit and would work for me. Goes to the top of my list.
Thanks.

I am surprised that you have a frame rub w/ 3.75" BS.

 

[bob p]

By now I'm sure you've realized that I've typed a lot without directly answering your question. Getting to the point then:

A 7" wheel with 12mm offset should fit a 225 tire safely with my setup, with NO rubbing.

If you decrease your offset from 12mm to 6mm, that's going to move both your inner and outer tire edges 6mm outward. If you decrease your section width from my target of 225 to 215, then you're pulling the tire's outer edges in by 5mm on each side. Without actually running the calculator, this tells me that:

With a 6mm offset and a 215mm tire, compared to a 12mm offset and a 225 mm tire:

a) the outer edge of the tire will be in the same place (ok, actually different by 1mm):

(225-215)/2 = 5mm inward displacement
12mm - 6 mm = 6mm outward displacement
net result: 6 - 5 = 1mm outward displacement (negligible)

b) the inner tire edge will move 10mm outward, giving you more clearance:

5mm outward movement of inner tire edge + 6mm less offset = 11 mm more clearance

In theory, your proposed wheel/tire setup should work beautifully with my spindle/brake setup. but I haven't actually done it, so I can't make any guarantees.

BTW, see how much easier it is to use the metric numbers for this sort of stuff?

 

[BigBoyzToyz]

I am surprised that you have a frame rub w/ 3.75" BS.


So am I! I have used 3 3/4" BS a lot, never rubbed any where. Are the tires quite large (wide) for the rims?

 

[roger1]

By now I'm sure you've realized that I've typed a lot without directly answering your question. Getting to the point then:

A 7" wheel with 12mm offset should fit a 225 tire safely with my setup, with NO rubbing. .....

Bob, thank you very much for the detailed analysis. Your setup is on my list and I will study it further.

Maybe it's in your info if I study it harder, but what is the wheel mounting width of your setup? I take it that it is a little wider than the stock 59.5"?

Roger

 

[bob p]

60.25". that's 59.5" plus 3/8 on each side.

its in my info, buried somewhere in those old posts.

 

[TinkerToy]

I have put all of the Brake posts in a single doccument as of 10-09-2009, 07:00 PM If anyone would like a copy of it please don't hesitate to email me randy@rbusinesssystems.com or send me a PM. it would be in a Word or .tf format.

 

[CJS57]

Nice write up bob. Just to be clear to future readers, all of your data applies to a 2" total dropped front end. If you drop it to 4" total down you will need more + offset. The other thing is you can get a near 7" x 14" wheel with a workable offset. Get a Wheelsmith 7x14" with a 4" backspace, for disc brakes. Send it to Weldcraft at the link below. Have them take 1/2" out of the frontspace. That will give you a 6 1/2" x 14 wheel with a +12 mm offset. It will run $200 per wheel when finished, not cheap but it will work.


http://www.weldcraftfab.com/