Jump to content
SAU Community

Why Have The Rear Lower Than The Front?

SS8_Gohan
 Share

Recommended Posts

SS8_Gohan Grand Master

SS8_Gohan

Posted
Posted

Just noticed in some of the threads, people are running their cars lower at the rear compared to the front. Ie, from centre of the wheel to the guard might be say 340mm and the front will be 350mm...

just wondering what the idea behind running different heights, front to back, is?? I think even the SK group buy might specificy different heights front/back

EDIT: sorry, thought i was posting in the suspension section, mods feel free to move if you think it's not in the best area

BHDave Grand Master

BHDave

Posted
Posted

it's because the front guards are typically cut 20mm higher than the rear.

So by running the center to guard heights 10mm less at the rear you actually end up with about 10mm of rake as the front is lower

260DET Experienced

260DET

Posted
Posted

Measuring and quoting comparable heights front to rear by the wheel gaps to the top of the guards is a bit off. Its usually and more accurately measured from under the body/chassis where a part is level with the ground front to rear eg sill panel.

Thanks for asking the question SS8.

djr81 Grand Master

djr81

Posted
Posted
Measuring and quoting comparable heights front to rear by the wheel gaps to the top of the guards is a bit off. Its usually and more accurately measured from under the body/chassis where a part is level with the ground front to rear eg sill panel.

Thanks for asking the question SS8.

It allows people to ignore the tyre diamater. Just about every Skyline ever built is running something different. They may only be 10mm out or whatever but it is enough to make a nonsense of the measurement. Unfortunately it makes the camber settings influence the result where previously they would not.

salad Veteran

salad

Posted
Posted
Unfortunately it makes the camber settings influence the result where previously they would not.

How so? I'm struggling to picture it... Camber makes the wheel pivot about the lower ball joint (for upper arm adjustment), so there's bugger all height change in the centre of the wheel, not even 1mm.

260DET: Sill measurements are best used to measure rake, but for actual ride height, centre of wheel to guard is better. As djr81 said, it neglects all differences in rolling diameters, so this includes things like wheel/tyre size and even tread wear (new tyres have 8mm tread)

Thunderbolt Rising Star

Thunderbolt

Posted
Posted (edited)

If you measure a stock car, you will probably find that the measurements are less on the back than they are on the front. When you lower a car, it is usually best to lower the car an equal amount front and rear. That is why you have probably observed this.

Edited by Thunderbolt
260DET Experienced

260DET

Posted
Posted
..............................................

260DET: Sill measurements are best used to measure rake, but for actual ride height, centre of wheel to guard is better. As djr81 said, it neglects all differences in rolling diameters, so this includes things like wheel/tyre size and even tread wear (new tyres have 8mm tread)

Get it now, thanks for the explanation.

It seems some people get confused, I've heard the 'lower at the back' claim before concerning rake. And thought WTF :dry:

salad Veteran

salad

Posted
Posted

I THINK the rule of thumb is lower front = better turn in. Quite happy to be corrected though.

I think it's to do with the centre of gravity heights front to rear, but then obviously suspension geometry starts playing a pretty big part in it too.

djr81 Grand Master

djr81

Posted
Posted
I THINK the rule of thumb is lower front = better turn in. Quite happy to be corrected though.

I think it's to do with the centre of gravity heights front to rear, but then obviously suspension geometry starts playing a pretty big part in it too.

Upside down Miss Jane.

Lowering the front will tend to generate more initial & indeed midcorner understeer.

Raising it will tend to allow the car to turn in better.

Sometimes it is a matter of balancing the turn in with the mid corner grip.

260DET Experienced

260DET

Posted
Posted

Rake helps the aero, providing of course it does not put aero aids such as wings out of alignment. High back particularly helps beneficial air flow under and out the back of the car.

SS8_Gohan Grand Master

SS8_Gohan

Posted
  • Author
Posted

ok ok... i haven't heard of rake before

so rake refers to the height of the front relative to the rear? So could you say a car has "positive" rake if the front or rear is higher?

To the cars have a default rake from factory??

So it's not such a bad thing to have the rear a little lower compared to the front? I like this as i've got a real low front spoiler, but my rear guards have the biggest "gap" between them and the tyre. So in terms of wheel guard gap, i could even it out a bit, but actually have the rear lower.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • oHBoy.
      Starter motor replacment teeth count.

      By oHBoy. · Posted

      I had 3 counts over the last couple of weeks once where i got stranded at a jdm paint yard booking in some work. 2nd time was moving the car into the drive way for the inspection and the 3rd was during the inspection for the co2 leak test. Fix: 1st, car off for a hour and half disconnected battery 10mins 4th try car started 2nd, 5th try started 3rd, countless time starting disconnected battery dude was under the hood listening to the starting sequence fuel pump ect.   
    • GTSBoy
      Mistakes were made, my R34 Story

      By GTSBoy · Posted

      This. As for your options - I suggest remote mounting the Nissan sensor further away on a length of steel tube. That tube to have a loop in it to handle vibration, etc etc. You will need to either put a tee and a bleed fitting near the sensor, or crack the fitting at the sensor to bleed it full of oil when you first set it up, otherwise you won't get the line filled. But this is a small problem. Just needs enough access to get it done.
    • suko
      J50 clock date suddenly reset to January 1

      By suko · Posted

      The time is always correct. Only the date is wrong. It currently thinks it is January 19. Tomorrow it will say it is January 20. The date and time are ( should be ! ) retrieved from the GPS navigation system.
    • MBS206
      Mistakes were made, my R34 Story

      By MBS206 · Posted

      Buy yourself a set of easy outs. See if they will get a good bite in and unthread it.   Very very lucky the whole sender didn't let go while on the track and cost you a motor!
    • Kinkstaah
      Mistakes were made, my R34 Story

      By Kinkstaah · Posted

      Well GTSBoy, prepare yourself further. I did a track day with 1/2 a day prep on Friday, inpromptu. The good news is that I got home, and didn't drive the car into a wall. Everything seemed mostly okay. The car was even a little faster than it was last time. I also got to get some good datalog data too. I also noticed a tiny bit of knock which was (luckily?) recorded. All I know is the knock sensors got recalibrated.... and are notorious for false knock. So I don't know if they are too sensitive, not sensitive enough... or some other third option. But I reduced timing anyway. It wasn't every pull through the session either. Think along the lines of -1 degree of timing for say, three instances while at the top of 4th in a 20 minute all-hot-lap session. Unfortunately at the end of session 2... I noticed a little oil. I borrowed some jack stands and a jack and took a look under there, but as is often the case, messing around with it kinda half cleaned it up, it was not conclusive where it was coming from. I decided to give it another go and see how it was. The amount of oil was maybe one/two small drops. I did another 20 minute session and car went well, and I was just starting to get into it and not be terrified of driving on track. I pulled over and checked in the pits and saw this: This is where I called it, packed up and went home as I live ~20 min from the track with a VERY VERY CLOSE EYE on Oil Pressure on the way home. The volume wasn't much but you never know. I checked it today when I had my own space/tools/time to find out what was going on, wanted to clean it up, run the car and see if any of the fittings from around the oil filter were causing it. I have like.. 5 fittings there, so I suspected one was (hopefully?) the culprit. It became immediately apparent as soon as I looked around more closely. 795d266d-a034-4b8c-89c9-d83860f5d00a.mp4       This is the R34 GTT oil sender connected via an adapter to an oil cooler block I have installed which runs AN lines to my cooler (and back). There's also an oil temp sensor on top.  Just after that video, I attempted to unthread the sensor to see if it's loose/worn and it disintegrated in my hand. So yes. I am glad I noticed that oil because it would appear that complete and utter catastrophic engine failure was about 1 second of engine runtime away. I did try to drill the fitting out, and only succeeded in drilling the middle hole much larger and now there's a... smooth hole in there with what looks like a damn sleeve still incredibly tight in there. Not really sure how to proceed from here. My options: 1) Find someone who can remove the stuck fitting, and use a steel adapter so it won't fatigue? (Female BSPT for the R34 sender to 1/8NPT male - HARD to find). IF it isn't possible to remove - Buy a new block ($320) and have someone tap a new 1/8NPT in the top of it ($????) and hope the steel adapter works better. 2) Buy a new block and give up on the OEM pressure sender for the dash entirely, and use the supplied 1/8 NPT for the oil temp sender. Having the oil pressure read 0 in the dash with the warning lamp will give me a lot of anxiety driving around. I do have the actual GM sensor/sender working, but it needs OBD2 as a gauge. If I'm datalogging I don't actually have a readout of what the gauge is currently displaying. 3) Other? Find a new location for the OEM sender? Though I don't know of anywhere that will work. I also don't know if a steel adapter is actually functionally smart here. It's clearly leveraged itself through vibration of the motor and snapped in half. This doesn't seem like a setup a smart person would replicate given the weight of the OEM sender. Still pretty happy being lucky for once and seeing this at the absolute last moment before bye bye motor in a big way, even if an adapter is apparently 6 weeks+ delivery and I have no way to free the current stuck/potentially destroyed threads in the current oil block.
×
×
  • Create New...