How low can you go ??

[forestb]

If I were kens65fb I would have given up on reading this thread a long time ago.

[SCOTI]

Originally Posted by forestb

If I were kens65fb I would have given up on reading this thread a long time ago.

Applicable information is still information.

My input was on highlighting the issue of clearances once one is curious about 'aggressive' lowering aka asking "how low can you go". Seemed related.

[short&wide65]

Originally Posted by SCOTI

You can disagree but tweaks made to the original 63-87 C10 geometry can change things completely; it just depends on one's definition of 'tweaks'.

There is nothing 'wrong' w/the stock set-up. It's not ideal vs. what's offered under current performance cars/trucks but neither are the aftermarket x-member kits being sold to achieve aggressive drop heights. R&P steering set-ups are an improvement over the original equipment steering box/set-up but only when everything is set-up & dialed in w/o compromise. Otherwise, it's just R&P steering that's easier to adapt to the raised x-member arrangement. A new perf spec steering box would also make a big difference in steering function.

If you're building something for autocross, using a Porterbuilt, GSI, Choppin Block, or Thorbeck Bro's raised x-member style set-up seems like a poor choice vs other more specific options. The aftermarket x-member kits do have updated geometry but again the OG stuff can be tweaked to rival the those offerings.

Autocross would benefit from a No Limit Engineering, Detroit Speed, SpeedTech, Scott's, or something from Roadster Shop (or maybe one of the very recently released to market QA-1 set-ups). These would be more aligned w/purpose built driving w/a nod toward autocross ambitions. They're also an even bigger investment vs. the aftermarket raised x-members.

So.... My question would be what do you consider to be 'just tweaks'?

I wasn't thinking about the raised crossmember setups and was thinking performance not "how low can you go" so I agree with you that Z-ing the frame is probably the best option. Never once have I thought about laying frame in my truck so I wasn't looking at the OP's problem correctly.

I was only thinking of No Limit's front crossmember since that is what I am going with. Of course I know there is an argument to be made that if I were truly serious about autocross I'd be looking at a full chassis instead.

But I have a full prep SCCA STR 2019 MX-5 and even with a full chassis, I'm not going faster at autocross in the 65.

Originally Posted by SCOTI

Applicable information is still information.

My input was on highlighting the issue of clearances once one is curious about 'aggressive' lowering aka asking "how low can you go". Seemed related.

Agreed. Always learning and discussing is what improves someone's knowledge.

[theastronaut]

Originally Posted by SCOTI

You can tweak the factory stuff to correct the Geometry. Tall BJ's, Caster mod, perf alignment vs stock spec, a new/faster ratio steering box, & lower center of gravity change things completely.

R&P set-up's are nice but again significantly add to the cost/complexity vs whats already there.

The setup I had on Goldilocks' build (stock crossmember raised 1.5", 1" narrowed PB tubular arms, .500" taller upper ball joints, and CPP Modular drop spindles) had more camber gain per inch of travel than No Limit's WideRide front end. Depending on how much body roll you have that could be a good thing or a bad thing. I like softer/more compliant suspension that absorbs mid corner bumps and curbing so having more camber gain to add more camber as the body rolls is a good thing- you can run less static camber. Stock camber gain is .86* per inch inch of travel, No Limit is 1.56*, my setup was 1.61*. The PB arms corrected the lack of caster and the No Limit rack & pinion corrected bump steer. The factory crossmember already has about 10* of antidive built in so that's good as-is. Now, if you like stiff suspension and no body roll because everyone thinks that's what makes something handle good... you don't really need geometry anyway, just throw some static camber at it.

The factory geometry with a few tweaks, plus an appropriate spring rate and good shock valving can be really good, and plenty good enough for autocross if you're not trying to be top level competitive.

[SCOTI]

Originally Posted by theastronaut

The setup I had on Goldilocks' build (stock crossmember raised 1.5", 1" narrowed PB tubular arms, .500" taller upper ball joints, and CPP Modular drop spindles) had more camber gain per inch of travel than No Limit's WideRide front end. Depending on how much body roll you have that could be a good thing or a bad thing. I like softer/more compliant suspension that absorbs mid corner bumps and curbing so having more camber gain to add more camber as the body rolls is a good thing- you can run less static camber. Stock camber gain is .86* per inch inch of travel, No Limit is 1.56*, my setup was 1.61*. The PB arms corrected the lack of caster and the No Limit rack & pinion corrected bump steer. The factory crossmember already has about 10* of antidive built in so that's good as-is. Now, if you like stiff suspension and no body roll because everyone thinks that's what makes something handle good... you don't really need geometry anyway, just throw some static camber at it.

The factory geometry with a few tweaks, plus an appropriate spring rate and good shock valving can be really good, and plenty good enough for autocross if you're not trying to be top level competitive.

I'm betting unless one has done the 'driver mod' (actually attended a driving school), the modded C10 set-up is more than enough for said driver.

[short&wide65]

Originally Posted by theastronaut

Now, if you like stiff suspension and no body roll because everyone thinks that's what makes something handle good... you don't really need geometry anyway, just throw some static camber at it.

Geometry does matter and a correctly damped suspension with stiff springs and sticky tires is faster so therefore does make something "handle good" Period. I am solely basing this on the stopwatch.

Originally Posted by SCOTI

I'm betting unless one has done the 'driver mod' (actually attended a driving school), the modded C10 set-up is more than enough for said driver.

Obviously, this is assumed. So the discussion is all things being equal.

[SCOTI]

Originally Posted by short&wide65

Geometry does matter and a correctly damped suspension with stiff springs and sticky tires is faster so therefore does make something "handle good" Period. I am solely basing this on the stopwatch.



Obviously, this is assumed. So the discussion is all things being equal.

I'm not assuming anything when I don't know who's using this info so the 'driver mod' mention is valid & useful.


But this is all off the original topic of how much lower @kens65fb can possibly go. My original concern was making sure he's aware of the pitfalls that extra inch or so of drop can yield.

Driving a truck that bottoms out a lot wears on you (& the truck/parts). I loved the ride height on my '74 but the constant bottoming out made driving any area where the roads weren't smooth a PITA thus much less enjoyable. Getting them lower than a 4/6 introduces those concerns. A 5/7 is do-able w/the right combo but will likely bottom out here & there. Again.... I was merely trying to promote awareness.

For reference, my CC dually is just as low as my '74 was but has adequate clearance. The 1.5" raised front x-member keeps it far enough away from the ground it's never bottomed out once it hit the roads 'post-mods'. Same for the rear of it.... It's never made contact w/the bumpstops or floor. The only thing that has made contact is the frame rails @ the center of the truck on funky angled entry/exit transitions of some parking lots. I have air so I could technically raise it but it's a coin flip on if it will/won't make contact so it isn't a common issue.

Everything I have is lowered & I won't build another aggressively lowered truck w/o necessary clearance. It's night & day difference IMO when it comes to a worry free driving experience.

[kens65fb]

I measured today.

The distance from the ground to the bottom of my front fender is 27 1/2 inches, it seems like 26 inches would look perfect

I'm curious, what is considered a perfect height.

Anybody else measured the distance from the ground to the bottom of the

fender ??

[forestb]

Have you looked through the photos of static drops thread? I would go through there and find one you like and then ask them their specs and for how they did it.

https://67-72chevytrucks.com/vboard/...ht=static+drop

[EricS76]

My measurement is 27.0, but I’m running a taller tire that fills the gap more. (235/75R15)

[txinliner]

im very late to this but my 65 has 3 inch belltech spindels 3 inch coils with a half coil cut in the front 5inch coils and inch and a half blocks

[forestb]

Originally Posted by txinliner

im very late to this but my 65 has 3 inch belltech spindels 3 inch coils with a half coil cut in the front 5inch coils and inch and a half blocks

Wow so is that like a 7 inch drop in the front and 7.5 in the rear. Are there no speed bumps where you live?

[raidmagic]

2.5 inch drop spindles and 2 inch springs in front and I was told 4 inch springs in the rear. I bought all the parts used and the guy was going by memory. 255-17r15 tires on factory truck rally wheels I've never measured to see how high the frame is off the ground.

[Shifty One]

Originally Posted by EricS76

My measurement is 27.0, but I’m running a taller tire that fills the gap more. (235/75R15)

Just an opinion, but taller tires look more "correct" with our body styles....(flame suit on)

[theastronaut]

Another example for reference. The front never rubs or bottoms out, plenty of travel and ground/tire clearance. No issues at at. The rear needs a c notch at this height; with trimmed bump stops the axle is only about 1.75" off the frame rail so bump travel is limited. I don't want to chop up the truck so I've tolerated the rear occasionally bottoming out on the bump stop. I used firmer rear shocks to slow down bump travel when empty, but when loaded with the camper shell or trailer it actually rides really well except over really big bumps. I'm looking into adjustable shocks to dial back the damping when it's empty.

Front-

CPP drop spindle/disc brake kit.
1 coil cut off stock springs.
Bump stop brackets completely cut off.
Stock drum brake wheels with 1.5" bolt on spacer.
215/75r15 tires.

Rear-

D2600 bags bolted directly to trailing arms, short upper cup to clear the air fittings.
1.5" drop blocks.
FrizzleFry's method of shock relocation.
Trimmed bump stops.
15x8 wheels.
235/75r15 tires.