Alternate ride height measurement question

[jhama78]

Gents, it seems to be standard procedure to measure from the fender above the center of the tire to the ground to establish a baseline for ride height. I understand that this is a good way to see how far you actually lower your truck after installing new suspension, but it really only is accurate on each vehicle individually because of tire size. Obviously if two trucks are running identical wheels and tires then the measurements could be more closely compared.

This brings me to my question... Has anybody measured from the fender to the center of the spindle or rear axle flange while doing suspension work? This would eliminate the tire diameter variable and allow more or less a direct comparison between trucks and ride heights would it not?

I could be completely off base here, but if I knew the spindle /rear axle flange center to fender measurements of say a 69 c10 with a 3\5 drop, could I not compare them to my stock sagged 67 measurements to see how much a similar set of springs would lower my junk?

If this has been discussed previously then please excuse my repost, but I'd be interested in hearing you alls opinions on my brainfart

[jhama78]

25 views and no opinions? I guess it is a bit to early on this holiday weekend for people to have imbibed enough to tell me that Im lol!

[SS Tim]

Used to do it all the time measuring test vehicles for spring sag. As you point out measuring from the center of rotation gives you a fixed repeatable spot independent of tire variations. But it must also be pointed out that bodylines vary between sides of a vehicle and between vehicles.
Of course while corner weight differences would also change the numbers some, it is a valid method to approximate an expected ride height. The closer vehicles "A" and "B" are in model and option content, the closer the result will be.

[lowrollin70gmc]

I've measured my 4wds many times using that method, as tire sizes vary much more than the 2wds see. It's the only way to measure and obtain a usable result.

The way I measure could vary a 1/4" or so, as I typically eyeball the hub centerline with the wheels mounted, as that's the only way to get true weight on the suspension components (along with a trip around the block). But I figure a 1/4" isn't much overall, as most guys are just looking for a ballpark number to make decisions off of.

Unfortunately, I don't have any numbers from my 70 GMC for you, as that one is bagged and on the ground.

[jhama78]

Thanks for the input gents, next time I'm in the garage I'll pull a tape on my 67 and post up the measurements. They're stock springs but I'm quite sure they have settled in the last 47 years

[67 cst swb]

Originally Posted by jhama78

Gents, it seems to be standard procedure to measure from the fender above the center of the tire to the ground to establish a baseline for ride height. I understand that this is a good way to see how far you actually lower your truck after installing new suspension, but it really only is accurate on each vehicle individually because of tire size. Obviously if two trucks are running identical wheels and tires then the measurements could be more closely compared.

This brings me to my question... Has anybody measured from the fender to the center of the spindle or rear axle flange while doing suspension work? This would eliminate the tire diameter variable and allow more or less a direct comparison between trucks and ride heights would it not?

I could be completely off base here, but if I knew the spindle /rear axle flange center to fender measurements of say a 69 c10 with a 3\5 drop, could I not compare them to my stock sagged 67 measurements to see how much a similar set of springs would lower my junk?

If this has been discussed previously then please excuse my repost, but I'd be interested in hearing you alls opinions on my brainfart

I agree with your theory... because a 28" tall tire vs. a 26" tall tire will effectively result in a different lowered measurement. That's why I appreciate when people post their lowering specs... that they list the components used such as 2.5" spindle with 1" spring or 2" spring, etc... and also the tire size they have. Then I subtract the tire size out of the measurement.
example:
235/75-15 tire
235 x .75 x 2 = 352.5 (which is metric mm) so to convert to inches...
352.5 divided by 25.4 = 13.877"
then you add the rim diameter in...
13.877" + 15" = 28.877" tall tire, then divide that in half for axle centerline to ground measurement...
in this case 14.438"
of course... the tire is not perfectly round as the weight of the vehicle is squaring off or flattening the portion of the tire in contact with the ground, so I typically round this measurement down to the nearest .25, in this case... 14.438" = 14.25"
Take the 14.250" off the measurement you have from the wheel arch to the ground and in my opinion, this will be the static drop in relation to the original ride height dimension of the vehicle.