Lowering, tire size questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

slotard · 03-05-2017, 12:35 PM

I have a '73 C20 Camper Special. It's high enough that it isn't easy to load bikes into it, and that's most of what I use it for. I'd like to lower it a little.

I currently have 30.5" tires on it (245/70-17), Michelins in great shape, on steel D hole wheels that I'm happy with. I'd prefer sticking with this tire size, as the gearing is short enough already and I don't want to make it worse (I have 4.10, need to swap a 3.73 axle that I have in but it still won't be great for freeway with no overdrive).

The rear I'm pretty sure I can drop no problem with the current tires (it's a utility bed so you guys probably can't tell me anyway). How about the front? Will I get rub if I install 2.5" drop spindles with 30.5" tires?

SCOTI · 03-06-2017, 10:37 AM

Quote:

Originally Posted by slotard

I have a '73 C20 Camper Special. It's high enough that it isn't easy to load bikes into it, and that's most of what I use it for. I'd like to lower it a little.

I currently have 30.5" tires on it (245/70-17), Michelins in great shape, on steel D hole wheels that I'm happy with. I'd prefer sticking with this tire size, as the gearing is short enough already and I don't want to make it worse (I have 4.10, need to swap a 3.73 axle that I have in but it still won't be great for freeway with no overdrive).

The rear I'm pretty sure I can drop no problem with the current tires (it's a utility bed so you guys probably can't tell me anyway). How about the front? Will I get rub if I install 2.5" drop spindles with 30.5" tires?

I'm not aware of any 2.5" spindles available for the C20/C30 spindles.

That being said, w/a mild 2-3" drop you should still have clearance for most smallish road irregularities but I'd bet you might buzz on some bigger dips when @ speed.

**MikeB** · 03-06-2017, 07:47 PM

I see where 1973 C20 inner and outer wheel bearings, calipers, brake pads, and tie rod ends are the same as used on C10 trucks with HD brakes.

Ah, ball joints are different. C20 must have larger diameter studs.

Just found these and others on eBay:

http://www.ebay.com/itm/C20-Drop-Spi...3D161806222240

slotard · 03-07-2017, 03:24 PM

I don't see how much those drop it, am I missing something?

SCOTI · 03-07-2017, 06:08 PM

Quote:

Originally Posted by slotard

I don't see how much those drop it, am I missing something?

I noticed that as well. All the info you need except the info you need

Ziegelsteinfaust · 03-07-2017, 07:39 PM

For a 3 inch drop use C30 drop spindle, and C30 calipers. Probably the best way for suspension travel.

As for dropping tires sizes, and using 3.73 gears. I would upgrade to a built 4L65 or better yet a 4L80. It will give you a much broader power band vs a different gear ratio

slotard · 03-08-2017, 03:24 PM

Is there anything else C30 I need besides spindles and calipers if I do that?

I'd like to LS swap it sometime, just don't have anywhere good to work on it right now.

03-05-2017, 12:35 PM	#1
slotard Registered User Join Date: Nov 2014 Location: Alameda, CA Posts: 877	Lowering, tire size questions I have a '73 C20 Camper Special. It's high enough that it isn't easy to load bikes into it, and that's most of what I use it for. I'd like to lower it a little. I currently have 30.5" tires on it (245/70-17), Michelins in great shape, on steel D hole wheels that I'm happy with. I'd prefer sticking with this tire size, as the gearing is short enough already and I don't want to make it worse (I have 4.10, need to swap a 3.73 axle that I have in but it still won't be great for freeway with no overdrive). The rear I'm pretty sure I can drop no problem with the current tires (it's a utility bed so you guys probably can't tell me anyway). How about the front? Will I get rub if I install 2.5" drop spindles with 30.5" tires? __________________ 1973 C20, 350/350

03-06-2017, 07:47 PM	#3
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,597	Re: Lowering, tire size questions I see where 1973 C20 inner and outer wheel bearings, calipers, brake pads, and tie rod ends are the same as used on C10 trucks with HD brakes. Ah, ball joints are different. C20 must have larger diameter studs. Just found these and others on eBay: http://www.ebay.com/itm/C20-Drop-Spi...3D161806222240 __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then! Last edited by MikeB; 03-06-2017 at 07:53 PM.

03-07-2017, 03:24 PM	#4
slotard Registered User Join Date: Nov 2014 Location: Alameda, CA Posts: 877	Re: Lowering, tire size questions I don't see how much those drop it, am I missing something? __________________ 1973 C20, 350/350

03-07-2017, 07:39 PM	#6
Ziegelsteinfaust Registered User Join Date: Dec 2012 Location: Temple City Posts: 3,628	Re: Lowering, tire size questions For a 3 inch drop use C30 drop spindle, and C30 calipers. Probably the best way for suspension travel. As for dropping tires sizes, and using 3.73 gears. I would upgrade to a built 4L65 or better yet a 4L80. It will give you a much broader power band vs a different gear ratio

03-08-2017, 03:24 PM	#7
slotard Registered User Join Date: Nov 2014 Location: Alameda, CA Posts: 877	Re: Lowering, tire size questions Is there anything else C30 I need besides spindles and calipers if I do that? I'd like to LS swap it sometime, just don't have anywhere good to work on it right now. __________________ 1973 C20, 350/350



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