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Rear disc brakes on american scion iq

15865 Views 70 Replies 8 Participants Last post by  jzchen
discuss.

i want this bad.

and a six speed but thats besides the point.

what would it take to get the rear discs available in europe fitted here in the USA? would you need a whole different rear axle for the mounting and routing of the brakes?
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I would almost wonder if the rear discs would need more or less brake line pressure from the master cylinder and whether the abs would screw things up too. This seems almost as nasty to do as getting a 6 speed from over there put into a US spec car.
Well, after getting nervous that Toyota discontinues the dust shields very early on, (Amayama is not able to get them for the conversion), I found a www.megazip.net said they are able to get them, and I pulled the trigger on parts I deemed necessary from both companies:

Axle: 42101-74020
*Dust Cover (RH): 47803-74010
*Dust Cover (LH): 47804-74010
Brake tube (NO.3): 47323-74020
Brake tube (NO.4): 47324-74020

* From MegaZip.

Now to sweat waiting to see that the parts come!!!

I realized afterwards I forgot this doesn’t include the calipers, brackets, and pads. Cheaper it seems to source here...
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this is for rear drum to disc conversion?

Well, after getting nervous that Toyota discontinues the dust shields very early on, (Amayama is not able to get them for the conversion), I found a www.megazip.net said they are able to get them, and I pulled the trigger on parts I deemed necessary from both companies:

Axle: 42101-74020
*Dust Cover (RH): 47803-74010
*Dust Cover (LH): 47804-74010
Brake tube (NO.3): 47323-74020
Brake tube (NO.4): 47324-74020

* From MegaZip.

Now to sweat the waiting to see that the parts come!!!

I realized afterwards I forgot this doesn’t include the calipers, brackets, and pads. Cheaper it seems to source here...
Yes.

The caliper, bracket, and pads I plan to get here as the parts are same as a Yaris as far as I know. The rest are unique to the rear disc iQ and are not available here in the USA from Toyota/Scion parts departments.

Forgot also need rotors!
I found out I was reading the wrong parts diagram and missed two hoses I'd need that are only available outside the USA, they are flexible hoses that connect to the calipers. Part # is 90947-02F96. Need one for each side. Just sent them a message asking if they could add them to my order! (Hopefully they don't get mad! First time I asked for a quote just for the axle, then realized I needed other parts and asked for a revised quote. They happily made a new quote for me with the extra parts. This time I already paid and two hoses have already arrived at their warehouse!
Not sure the real reason you want to do this, but you probably won't see much braking improvement as the front brake does most of the stopping work. In fact, you may even make it worse with the rear disc providing more stopping power than the front. the whole abs/traction control system may not be too happy with that.

the easiest way to improve braking is to get sticky tires and better brake pads.

good luck

Yes.

The caliper, bracket, and pads I plan to get here as the parts are same as a Yaris as far as I know. The rest are unique to the rear disc iQ and are not available here in the USA from Toyota/Scion parts departments.

Forgot also need rotors!
Very true.

One thing that has made things complicated is my ability to read the parts diagrams. I have been confused, because on the parts descriptions the applicable month and year is typed: MM, YYYY. On the top left of the parts diagram it is opposite, and I didn’t understand this until maybe Thursday! Format is YYMM!

Early on I compared the brake booster and brake master cylinder part numbers, trying to see if there’s a difference whether rear drum or disc. I do believe I may have made a mistake In interpreting the rear drum models and rear disc models have the same master cylinder part #.

Drums last a very long time. But I am not good at servicing them, along with stories about them getting stuck, and you can’t easily see the status of the linings nor the drum wear without disassembling, headache.

I am lucky in that my wife scheduled a trip and we will be visiting Japan for a little bit this summer. I was hoping to work out any issues with this project during the visit, which pushed me onwards, besides the dust shield availability concern.

On my experience with the two companies:

Amayama as of Friday has completed collecting the parts I ordered from them. I do believe I may have caught them in time to possibly hold them until they can get the two flexible hoses, I hope. There’s no promises but they will try. They have also been excellent communication wise as they respond extremely quickly to my requests.

MegaZip has been excellent with respect to communication as well. There is a slight delay from end of Feb to beginning of March for the part arrival at their location, but that makes perfect sense because of the time difference, I did not order the same day. I ordered a day or two later, (hesitant as one company already notes they are not available). I was also asked whether I would like to wait or not. These dust shields are the parts that Toyota seems to discontinue early on. I’m already impressed because Amayama says “N/A”.

I have some available aftermarket rear disc part numbers I have compiled. This is through cross reference of the Toyota part number. My son has a Science Olympiad competition today so I’m going back to bed for now and will post them later....
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here is my 2 cents.

The entire brake/ABS/traction system is calibrated based on the factory setup. the results may not be what you expected by just altering the stopping mechanism on the rear (drum to disc) without proper calibration. Most if not all people would improve the front with either better pads or larger disc and it is more management as far as handling goes. If your rear locked up during turns or wet weather, it is game over especially with such a short wheel base car.

I would probably spend the effort/money on something else like better tires/wheels, springs/shocks/sway bar, front disc/pad etc....

It is your money and time... :)

Very true.
Well, thank you for your advice. I’m afraid I already set things in motion and will either deal with the consequences or let the parts sit while I sort out what to do with them. Still concerned about the master cylinder part number being different from the one on the USA parts site. I did not order one of those and they are quite expensive....
I found 3 different part numbers for the master cylinder, as well as 3 for the brake booster.

There’s a pair for the USA, a GAZOO Racing set, and a third set that apply. This is going off the parts.toyota.com website and the Amayama link to Toyota EPC data that seems to come from a Russian site. As far as I can tell the GAZOO version is specific to a special edition that they tuned with a high output (turbo) engine. Of course the USA parts are specific to LHD and drum rear. So the (RHD) EPC shows both a drum and disc option for the rear, but does not specify any other specific parts for drum vs disc. It does specify slotted front rotors and different booster, master cylinder, one “tube”, among others, as GAZOO specific.

It seems I’ll be okay with regards to proportioning from this research.

Haven’t quite sorted out the proper discs and calipers yet....
So I've mainly worked on researching rear disc rotors so far. The Toyota part # is 42431-52080. Per the Toyota Parts Website:

https://parts.toyota.com/p/62919221/4243152080.html

It fits 2012-2015 Toyota Yaris with rear disc brake option.

I wasn't feeling very confident that the aftermarket manufacturers were correct in their application guides, so I started with whatever I could find using cross reference to 42431-52080. Here's a list of what cross:

BeckArnley: 083-3629
Wagner: BD180541
Bendix: PRT6183
Centric: 120.44183
C-TEK 121.44183
Slotted 126.44183SL (left)
Slotted 126.44183SR (right)
(there is cross drilled I believe but not interested I did not note them)
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All parts ordered from Amayama are on their way, including the extra order I added to it, which delayed it some. (Completely my fault). Plus it doesn’t note any increased shipping. (Very nice of them)! Tracking notes should be here on the 7th! That’s FAST!!!

Wonder what source MegaZip is getting the dust shields from, that they can get them but Amayama can’t.....
Big package with the axle is in Oakland, CA, with expected delivery by 8:00 pm today....
how much for all the required parts for the conversion?

Big package with the axle is in Oakland, CA, with expected delivery by 8:00 pm today....
I didn't purchase all the parts yet so I'm afraid I don't have an exact answer. (I'm suspecting there may be some bolts and clips that I may need along the way). I still haven't decided on/bought brake calipers, rotors, and pads. www.brakeperformance.com seems to have a nice set of rotors and pads, for a Yaris/not cross reference. I am hoping that they will fit. Actually seems cheaper to buy them combined, than to buy the rotors alone... So far Amayama total is $933.11, which includes $220 for shipping FedEx. Based on speed I'm confident the box got to ride in a plane, vs ship transport across the Pacific Ocean. A little worried that the $50.30 I paid to the other company for the dust shields may not pull through. Status is still paid but not shipped. I did find the axle (the main cost) at a local vendor in Chino I believe, for a whopping $1582.36 here:

https://www.scuderiacarparts.com/part/259691/astonmartin/4210174020/beam-assy-rear-axle.html

I'm still ahead with respect to their pricing. (Even before adding tax)....

The package did not arrive, although early this morning package is noted in Los Angeles. I can't sign for it today as I've got to go help in a school orchestra performance at another school. (Got to help pack the instruments into a trailer and chaperone). Apparently Trump is at peace with regards to trade with Japan. No notice of any import duty due and package made it to LA. My research tells me that at maximum I'd be charged 2%, but it is likely no charge.
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The dust shields were shipped over the weekend and are in Los Angeles from the EMS tracking. Kudos to MegaZip for getting me those hard to find parts!!!
Everything from Japan here. Axle poked holes through the box in a few places. Gonna touch-up with some black touch-up paint.



Cool, was not charged any import duties/taxes!
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