Rear coilover kits and tire size limitations?

[siggyfreud]

Hey all,

I'm about to get some custom forgeline wheels for my truck. Right now I'm on coil suspension, at about the ride height I intend to keep (previous owner). That said, I'd like to shift over to coilovers. When looking at various kits, it appears all except for RideTechs have the coilovers on the outside of the frame rails.

Should I be concerned about tire width interfering with them? My assumption is yes, since currently I have wider tubs, and the amount of space I have is only limited by the frame. I intend to run a 315 tire on an 11 or 12" wheel, but not sure if I need to worry about whether that leaves room for an outboard coilover, or if I'm limiting myself to a ridetech supet in the future.

This is on a 72 c10. Anyone run into this dilemma?

Thanks!

[mongocanfly]

I don't see any issue with having the coils inside the frame...if your getting custom wheels I wouldn't do a thing till you get the wheels and tires and see where your clearance is
you can lean the coilovers to the inside at the top..you just need a good stout crossmember
heres pbf showing inside the frame

[68Stepbed]

I have the [url=https://totalcostinvolved.com/products/1963-1972-chevy-c10-torque-arm-rear-suspension/]TCI[url] rear torque arm setup that happens to have the coilovers mounted outboard. Even with my narrow stepside fenders, I still have room for 18x11s with 315 tires. If I had a fleetside, 18x12s and 335s would be no issue. I will say, however, that the shock mounts are my limiting factor to running the 12" wheels with 335 tires on my truck.

There are advantages to outboard mounted coilovers vs inboard. The outboard mounts provide more cornering stability since that's where all the weight transfer is going. Somebody smarter than I am can explain it better. I do know that my setup is amazing and I'm winning events.






https://www.youtube.com/watch?v=9W4Jkh2XGCI

[siggyfreud]

Thank you both for the input. My preference would be to run an outboard setup for the advantages 68Stepbed mentioned. Having those coils further from the pivot point should add more stability, allow it to rotate less, and make their work easier. Just wanted to know if I was backing myself into a corner if I went with 12" wheels. Guess I'll measure today and see what type of offset I'd need and space I'd have left with a 12 wheel.

I'll have the tool soon to actually have a tire mounted under there and see what space I have.

[68Stepbed]

Originally Posted by siggyfreud

Thank you both for the input. My preference would be to run an outboard setup for the advantages 68Stepbed mentioned. Having those coils further from the pivot point should add more stability, allow it to rotate less, and make their work easier. Just wanted to know if I was backing myself into a corner if I went with 12" wheels. Guess I'll measure today and see what type of offset I'd need and space I'd have left with a 12 wheel.

I'll have the tool soon to actually have a tire mounted under there and see what space I have.

So, you plan to order wheels before suspension?

[siggyfreud]

Originally Posted by 68Stepbed

So, you plan to order wheels before suspension?

Yeah, I kind of have to at this point. I'll likely be moving soon, and have no wheels/tires for this, so it's up on jacks. My previous set didn't clear the front big brakes, so couldn't have even put those back on. I don't have the cash at the moment to do both wheels/tires and suspension, and I don't really want to spend cash on a temporary wheel/tire set either.

That said, the height the truck is at is the height I'd like to keep it at/around (~4/6 drop) so I'm not all too concerned from a clearance perspective, other than just the coilover, or lower coilover mount on an outboard setup.

But if you're saying you can run 11"-315 wheels/tires on your step fenders, I should be good with my fleetside. I don't really need to go wider than that. The previous setup back there was a 305/55/R20, and it fit, I just can't remember how much room there was between the tire and where outboard suspension would mount.

If it does end up limiting my suspension choices to inboard coilovers, I am OKAY with that, just not ideal, but I suspect once I measure I'll find I have room. But again, if the worst thing I end up with a rear ridetech suspension setup, it'll still be miles better than what is there already.

Think I'm shooting myself in the foot?

[siggyfreud]

Looks like from the wheel mounting surface I have about 6" of frontspacing, and 9.5" of backspacing, for a total of about 15.5" of width area for a wheel and tire. Also looks like I have a few extra inches beyond that for suspension, however with the way the previous owner ran the exhaust (outside frame rails) I'd have to redo the exhaust to make room for coilovers, which isn't a huge deal.

[68Stepbed]

Originally Posted by siggyfreud

Yeah, I kind of have to at this point. I'll likely be moving soon, and have no wheels/tires for this, so it's up on jacks. My previous set didn't clear the front big brakes, so couldn't have even put those back on. I don't have the cash at the moment to do both wheels/tires and suspension, and I don't really want to spend cash on a temporary wheel/tire set either.

That said, the height the truck is at is the height I'd like to keep it at/around (~4/6 drop) so I'm not all too concerned from a clearance perspective, other than just the coilover, or lower coilover mount on an outboard setup.

But if you're saying you can run 11"-315 wheels/tires on your step fenders, I should be good with my fleetside. I don't really need to go wider than that. The previous setup back there was a 305/55/R20, and it fit, I just can't remember how much room there was between the tire and where outboard suspension would mount.

If it does end up limiting my suspension choices to inboard coilovers, I am OKAY with that, just not ideal, but I suspect once I measure I'll find I have room. But again, if the worst thing I end up with a rear ridetech suspension setup, it'll still be miles better than what is there already.

Think I'm shooting myself in the foot?

As long as you take into consideration to get enough offset to allow for the coliovers in the future, you should be ok. I understand the ideal of having to stay in budget. That's why I'm still on 9.5" wheels and 275 tires. My budget just won't allow for custom wheels.

Originally Posted by siggyfreud

Looks like from the wheel mounting surface I have about 6" of frontspacing, and 9.5" of backspacing, for a total of about 15.5" of width area for a wheel and tire. Also looks like I have a few extra inches beyond that for suspension, however with the way the previous owner ran the exhaust (outside frame rails) I'd have to redo the exhaust to make room for coilovers, which isn't a huge deal.

Below are some photos of my fitment process to determine what I needed for 18x11 and 315/30/18 tires. Keep in mind the stepside beds are more narrow than fleetsides. I came up with 6.75" backspacing for my setup. You can see how much it fills up the fender and how close it is to the lower shock mount. On the fleetside, you could easily get away with 6.5" backspacing and still have room for outboard coilovers, but I'd still use a wheel fitment tool to ensure proper backspacing. Keep in mind, all these measurements are with a stock width 72 rearend. If you have a 67-70 rearend, all these numbers will change!

[siggyfreud]

What size tire is that fitting up in the front?

And for the rear, how far inset from the fender lip are they? My rear fenders have rub marks from the tire on the outside, but they were also huge 305/55/R20, so I think it was a matter of the 305s being much taller. When I did some measuring last night I was probably giving myself too much backspace and moving it too far from the outer fender, which would look off as your pictures they look almost flush and that looks right.

[TTurbo565]

you should have no problem running outside the frame coil-overs with a 315 tire. I am running 345/30/19 with a 12 inch wheel on the rear of my C10. I have the No Limit trailing arm setup with Ridetech coil-overs and there is a ton of room.

[siggyfreud]

Any more shots of that 345? Perhaps from the side? I'd love to run that width, but man tire selection gets really limited up there. For a non-track-only tire it seems like Super Sports and Sport Cup 2s are the only semi-streetable tires. What backspacing are you on with those 12" wheels?

[TTurbo565]

The tire is a Super Sport. The bs is 8.35" (47mm offset) with a two inch spacer. They were originally set up for a Corvette. they have 5X4.75 bolt pattern. Interchangeable with my other car. I had the pattern changed on the axle as well to run the C5 brakes.

[siggyfreud]

So would that make the realized backspace about 6.35, since the spacer would shift two of those inches outward again?

[TTurbo565]

yes, that would be 6.35 inches of backspacing. there is a little added offset in the axle width because of the rotors instead of drum brakes, but it is very minor. To fit the larger tires you will need to cut the wheel Tubs and bed to make room. I have a wood bed so it was really easy for me. I left 48 1/2 inches between tubs so I can still fit a 4 X 8 sheet of plywood. It will rub a little on excessively angled drives and even sometimes when I am utilizing the suspension. a roll bar would probably cure that. to get it to really handle you will probably want one anyway.

[68Stepbed]

Originally Posted by siggyfreud

What size tire is that fitting up in the front?

That's also the same 18x11 and 315 up front, also with the same backspacing. Yes, I can run a true, squared 18x11/315 setup.

[siggyfreud]

Is that primarily due to the tci front end?

[68Stepbed]

Originally Posted by siggyfreud

Is that primarily due to the tci front end?

Yes. My current 18x9.5 wheels barely fit with the stock suspension. The TCI control arms are a bit more narrow, and with the rack & pinion and sway bar style, there's quite a bit more room. I could actually go 18x12 with 335s in front, but again, the rear is my limiting factor.

[siggyfreud]

Originally Posted by 68Stepbed

Yes. My current 18x9.5 wheels barely fit with the stock suspension. The TCI control arms are a bit more narrow, and with the rack & pinion and sway bar style, there's quite a bit more room. I could actually go 18x12 with 335s in front, but again, the rear is my limiting factor.

Good to know . . . damn maybe I need to consider doing the TCI front sooner just so I can go wider in the front. I was thinking 295, but if I could get a 305 up there I'd be really happy with that.

[68Stepbed]

Originally Posted by siggyfreud

Good to know . . . damn maybe I need to consider doing the TCI front sooner just so I can go wider in the front. I was thinking 295, but if I could get a 305 up there I'd be really happy with that.

I'm always willing to help people spend their money!!

[siggyfreud]

Alright, did some measuring with the wheel tool and some tires. I'll be giving GoMobileTiresPDX a better plug in a video later, but the owner was super cool and helpful, and their setup was incredibly clean. Their mount systems are touchless on the wheel, which is nice.

Anyways, looks like I can do a 20x11 - 315/35R20 with about a 6.75" BS on all 4 corners. In the fronts, it cleared the LCA fine, but the tire did rub the shock at full lock right turn. But, when I go to a coil-over setup in the future I won't have that issue, and for now, I just have to remember at full lock I'll get some rubbing, which will, fortunately, be low-speed which I can avoid.

I can see where an 18x11 wouldn't have cleared the front LCA though, as I have about 1.25" of clearance likely just due to the wider diameter wheel size.

[siggyfreud]

I started at 6.5" BS, but looking back at some of the photos I feel like they look a little too tucked, and could come out further. I might even consider 6.25", as at 6.75" I think they'd still look more tucked than yours do 68Stepbed. Some of my photos got wacked. In this one the width wasn't tightened down enough, and the tire pulled the simulated rim width into about a 10.5" wheel. And this was 6.5" BS. So if I add the .5" width back in, and shifted the wheel out .5", I feel like it would look about right in terms of distance to fender.

Thoughts?

Edit: After measuring again, minus tires, I feel like I should stick with 6.75". I can't bring them out too far, and I think losing that extra .5" might just be borderline.

[68Stepbed]

I need to ask an important question. What is the end purpose for this truck? I ask because of tire selection. 20's will offer plenty of sizes, but actual "performance" tire sizes are limited in 20's

[siggyfreud]

Spirited DD honestly, and future "shop truck." My commutes outside of work tend to be a mix of highway and some fun twisties, so something that takes the mundane out of the road is helpful. I've had some track-ready cars in the past, like a GT350, so I can definitely discern something that handles well from something that doesn't, but my time for the track is definitely limited these days.

I'm happy with the tire selection available in that size range honestly. There are plenty in the 315/35/R20 range with everything from Nitto, Pirelli, Contis, and Super Sports. There are even some drag tires I have found should that call to me.

I'll probably start with some Nitto 555s to keep the budget in check for now though. But my tire guy will give me a heads up if anything goes on sale between now and when I order.

I ended up going with 20x12 in the rear with a 7.75" BS, and 20x11 front with a 6.75"

[68Stepbed]

Originally Posted by siggyfreud

Spirited DD honestly, and future "shop truck." My commutes outside of work tend to be a mix of highway and some fun twisties, so something that takes the mundane out of the road is helpful. I've had some track-ready cars in the past, like a GT350, so I can definitely discern something that handles well from something that doesn't, but my time for the track is definitely limited these days.

I'm happy with the tire selection available in that size range honestly. There are plenty in the 315/35/R20 range with everything from Nitto, Pirelli, Contis, and Super Sports. There are even some drag tires I have found should that call to me.

I'll probably start with some Nitto 555s to keep the budget in check for now though. But my tire guy will give me a heads up if anything goes on sale between now and when I order.

I ended up going with 20x12 in the rear with a 7.75" BS, and 20x11 front with a 6.75"

You should be fine, then. Autocross and road race tire development has made leaps and bounds the past few years. The issue I've seen is they work well for one thing, and normal street use isn't one of them.

I try to ask anyone who is building a Pro-touring style vehicle what they plan to do. I've witnessed several people order custom 20" wheels then go start autocrossing or road racing, but they can't be competitive because they can't get the proper tires.

[71cheyennesuperlongb]

What size wheels have the best assortment of stickeys? I just bought Robs suspension package for my daughters 71 shortbed and any advise would be helpfull.