YZF or Thunderace front wheel

[RempageR1]

Hi,

I`m looking for a direct swapover rim for my original`93 front end. I am already running R1 rotors and calipers so anything that could take those without any modification would be great.

From what I read, Thunderace would work but I also heard R1`s would work. The latter however doesn't seem to be able to take the speedo pickup so I guess it`s not a really 1:1 swap. Any advice for a 1:1 swapover would be appreciated. Thanks!

 

[RempageR1]

So from what I found, it`s going to be hard to fit a tyre on those 17 inch rims that will be both wide and have a diameter that is close to original. Are there any 18 inch alternatives that would work? Thanks.

 

[02GF74]

if you have found the correct wheel/tyre combo then there is no need to compromise. you will need some sort of adapter to drive the speedometer at the correct rate. there are another of solutions, but the one that springs to mind is a gearbox that alters the drive ratio.

a quick google throws up this: - based in US ... which I notice is not where you are ... i'm pretty sure I came across a company base in UK that did similar.

https://transmissioncenter.net/shop/ratio-adapter-other-ratios-available-call-jim-1-888-2012066/

if you had access to machine tools, it probably would not be difficult to make an inline gearbox.

the cheapskate solution is to print a new facia for the speedo but the odometer will be out.

 

[MaxMidnight]

Not sure there is a direct OE wheel replacement nor do I recall a Thunderace wheel being fitted.
The Thundercat front will fit but does require minor modifications. If you use the Tcat speedo drive then your speedo will be OK.

 

[02GF74]

If you use the Tcat speedo drive then your speedo will be OK.

I hate to disagree but I don't see why that would be the case. Assuming there is no gearing inside either speedo, then for any rpm of the cable, the needle will move to a specified position. The numbers on dials would therefore need to be in the same position; whuch they aren't - image below shows needle when moved 180 degrees which shows different mph values.

 

[MaxMidnight]

I wrote the speedo drive not speedo.

The indicated speed is shown by the deflection of the speedo needle which is governed by how fast the cable is turning (stating the obvious I know).
How fast the cable turns is determined a) by the rolling radius of the wheel and b) the ratio between the driving and driven gears in the speedo drive.

Change any of those variables and the indicated speed will change relative to the actual speed.
As the rolling radius of the wheel and the numbers on the dial are fixed (assuming you don't change the relative positions of the numbers) then the only other potential variable is the gear ratio's within the speedo drive.

With the original speedo and drive then one rotation of the wheel a wheel with a smaller rolling radius will not turn the speedo cable as many times and thus the speedo will under read.

 

[02GF74]

Indeed , you did indeed say speedo drive, my bad for not spotting that.

 

[RempageR1]

Thanks all for the help. I did some research and it seems the Thunderace and Thundercat have the same front wheel. Their partnumbers are 4SV25168007B
and 4TV25168007B, where 4SV and 4TV stand for the Thunderace and Thundercat resp. Pictures and markings on both rims are also identical.

If I look at my current front wheel, the brake disk bolts are very near to the fork legs as it is. Less than a mm on the left-hand side. Is this normal?

Finally, the speedo drive is argued to have the same ratio as the Vmax one has on the vmaxchat link. Can anyone provide some more detail as to weather the difference is indeed in the clocks or the speedo drive?

Thanks!

 

[Traumahawk]

As far as speedos go, I like Seans GPS speedo. That way no matter what wheel you, you dont have to worry about drives or gears.

 

[MaxMidnight]

Note that Yameringha use the same number, in this case 25168, to indicate what the component is i.e. a front wheel.
The T.cat wheel is 4TV-25168-00-7B whereas the V Max is 2HY-25168-00-P0.
Note they share the same part identifier but we know they are not the same part.
On that basis you cant be sure that the T.cat and T.ace parts are identical or are interchangeable.

Same goes for the speedo drive, they have the same part identifier but different model code therefore you can't assume they are the same.

IMO parts that are common across model ranges would have the same part number...I could be wrong here though.

Many moons ago I had both Max and T.cat speedo drives and they were different ratio's. Unfortunately I didn't make any notes so can't confirm what the difference was.

 

[dannymax]

The Thundercat speedo drive has a smaller diameter axle than the VMax but the internal gearings are interchangeable. This requires drilling and punching out the blind plug in the housing to remove the gears, or bore the housing.

 

[MaxMidnight]

I don't think that is correct Danny.
The T.cat speedo drive I bought had the same axle diameter (17mm) as the Max and all the fitting instructions I have seen makes no mention of changing the axle.

 

[02GF74]

As far as speedos go, I like Seans GPS speedo. That way no matter what wheel you, you don't have to worry about drives or gears.

that's all fine and dandy until the Russians start shooting down the GPS satellites

 

[MaxMidnight]

that's all fine and dandy until the Russians start shooting down the GPS satellites

If its got to that stage I suspect the last thing you will be worrying about is how fast you are going.

 

[dannymax]

I don't think that is correct Danny.
The T.cat speedo drive I bought had the same axle diameter (17mm) as the Max and all the fitting instructions I have seen makes no mention of changing the axle.

Steve, I got a speedo drive off eBay for a YZF600 to use as a gear donor...would that drive have a smaller axle? Or maybe it's just a memory thing...that was a lot of carburetor cleaner fumes ago....??

 

[maleko89]

If the Tcat is equivalent to the YZF600R in the U.S., then front axle diameter is 19 mm.

Mark

 

[Traumahawk]

Steve, I got a speedo drive off eBay for a YZF600 to use as a gear donor...would that drive have a smaller axle? Or maybe it's just a memory thing...that was a lot of carburetor cleaner fumes ago....??

That might be true, but Ive met you in person and chatted over the phone. I STILL think that your sharper than 95% of all of the people out there.

 

[02GF74]

Finally, the speedo drive is argued to have the same ratio as the Vmax one has on the vmaxchat link. Can anyone provide some more detail as to weather the difference is indeed in the clocks or the speedo drive?

If the drive ratios are the same, then the cable will turn at the same rate when riding at the same speed with the same tyre circumference.... and despite what I said above, both speedo will show the same speed.

Because inside the speedometer, is a magnet inside a metal cup that is rotated by the cable. When the magnet turns, it induces a magnetic field in the metal cup which is prevented from turning by a metal spring. The faster the magnet turns, the more the cup wants to move. Fit a pointer to the cup and you have an indication of how fast the cable is turning.

So although the markings on the dials are different, all that means is the magnets are of different strength to cause a different deflection at the same cable turn rate.

In short, if the new wheel is the same circumference and the speedo drive is same ratio, the existing Vmax speedo will show mph correctly.

Otherwise options are:
1. an inline gearbox to change cable turn ratio
2. have the magnet inside the speedo remagnetised
3. fit gps speed
4. convert to electronic pick up and either have a motor drive the Vmax speedo of fit an electronic speedo

If it were me, I'd look at 1 and 2 to keep the original speedo

 

[MaxMidnight]

In short, if the new wheel is the same circumference and the speedo drive is same ratio, the existing Vmax speedo will show mph correctly.

But we know they are different; the circumference of the Max tyre is 81.037 inches and the T.cat is 71.27. Therefore we know it will over read by about 12% with the T.cat front.

If the Tcat is equivalent to the YZF600R in the U.S., then front axle diameter is 19 mm.

My guess is that it isn't as there is no need to alter the axle with the T.cat wheel...although you do need to change the axle when fitting a Diversion rear.

 

[02GF74]

But we know they are different; the circumference of the Max tyre is 81.037mm and the T.cat is 71.27. Therefore we know it will over read by about 12% with the T.cat front.

Are we talking about scale models?

I know when I was working on my self-cancelling circuit I calculated the circumference to be almost exactly 2.0 m; Those dimensions are for a 1/24 scale model.

Suffice to say, the speedo will over read, bearing in my speedometers by law (in UK) have to over read anyway.