Sc400 abs brakes and sensors

Lambo

Moderator
Hi Guys, I am still beavering away on my project with the brake /upright change, I have a set of Supra uprights, that have the ABS toothed wheel mounted behind the drive flange, it has 96 teeth, and I have the original Soarer upright, that has it's toothed wheel behind the axel shaft it has 48 teeth I would prefer to use the Supra upright as the steering arm is 25mm shorter than the Soarer version.
Does anyone know what the change from a 48 to 96 toothed wheel will do to the ABS the pitch and size of the teeth are the same, it's just the Supra has double the number.
Does the ABS computer just expect to see a pulse at a constant rate, so when the wheel locks up under braking the ABS ecu just pulses the brake peddle until the pulse returns from the wheel, so the number of teeth is not important or will I have to install a pulse divider circuit to fool the computer into thinking it only has 48 teeth as original, I have followed out the wiring diagram and the ABS ecu seems to take a speed signal from the cluster so I wonder if the ecu will be confused by the extra teeth, when it is taking a reference speed from the cluster. I have spent hours trawling the net for an answer without luck, does anyone have any knowledge or experience on this subject.

Best Regards
Lambo
 

gloverman

Well-Known Member
I would be matching all the teeth counts up. Also wire up the diagnostic port so you can monitor what the ECU sees.
 

Lambo

Moderator
Thanks guys for your help, If I can't find an definite answer, I will just go with the original Soarer then it will match the ABS ecu and the original rear sensors etc , as brakes are somewhat important.
The Supra upright with the shorter arm came from a MA/GA70 it measures very similar but has different brake calliper mounting holes and a bigger drive flange, so Soarer disks will not fit. This means it could be re drilled to my bigger wheel pcd so no adapter required, but then you can't fit 4 pot brakes, the shorter arm would mean quicker steering, but new disks could be hard to get now and in the future, and they are thinner than the Soarer units.
Why does life offer so many confusing choices lol
Regards
Graeme
 

Lambo

Moderator
ABS and upright issues

Hi Blackuzz31, Interesting you should say that, I have the Soarer suspension x member etc all setup on my build board with the Soarer upright.
I then swapped over to the GA70 I expected the KPI or something to be a major difference, but that was not the case, I checked the KPI with a digital protractor and it was the same. I also checked the hub face , have I missed something, I have included some pics the first are the Supra the second the Soarer, the two uprights over all measure within a few mm of each other, but the biggest difference is where they put the stub axel relative to the kpi viewed from the inside, the Supra axel centre is about 15mm in front of the kpi, and the Soarer is 10mm behind, so given the bottom and top suspension arms stay in the same place this would have a major effect on the wheelbase, this is not a problem through as the bottom and top arm can be moved to correct that.
I originally measured from the centre of the axel to the pivot on the steering arm and the Soarer measured 140 mm and the Supra 110mm, but I wasn't till I put the two side by side to take the photos, I realised the distance from the kpi to the steering arm pivot was identical at 130mm so there is no advantage to use the Supra upright to get quicker steering because relative to the kpi they are identical. so I think I will make life simple and just use the Soarer upright. I just wish I knew why the axel is in a different position.
I am going to be using the Soarer top and bottom arms they are its a little shorter than the Supra, I have Suspension Analyser to feed it all into so if it is going to cause problems, I can modify the suspension mount points to compensate, I will be using the GA70 rack also, it’s a power rack and I found out the other day I can shorten the passenger end of the rack and rethread the tie rod end in the rack, and then shorten the main hydraulic tube to suit.
Do you have any thoughts about the fitment of wheel adaptors, the Countach wheels I am using have a pos 20mm offset, and are 15 x 81/2 I have a set of what I assume are Supra rims that came on the totalled Soarer, they have a offset of 50pos stamped on them and are 16x 8 .pic attached
Do you know the factory original offset and size of the 1991 UZZ31, some sites suggest they were 38-45mm , I plan on having a 23mm adaptor with a 20mm offset Countach wheel so that puts me at 43 very close to what I believe the Soarer may have had.
Best Regards
Graeme
 

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