Modern tire size.....78z1r

I've been trying to figure out what the ideal modern tire size is for my 78 Z1R? Stock size is 4.00-18 rear and 3.50-18 front....I've had the forks built up, ordered a swinger from trac dynamics, and will be going with modern shocks.....so the last thing I wanna do is hurt handling......I plan on riding it a lot and fairly aggressively....not track aggressive but I want it to handle well. I'm leaning towards Pirelli sport demons.

What sizes have been good for other members?


Cheers

My bike came with the same size stock rear tire as yours. I run a 120/90 V 18 Sport Demon on the rear, and it is the correct size tire. In the past I ran 130/90 V 18 tires on the rear. They work, but because they are a bit too wide for the rim the cross-section of the tread ends up being a bit distorted and they don't work any better than the 120 size.

My front tire is a different size than yours (3.25-19 instead of 3.50-18). I run a 100/90 V 19 Sport Demon on the front of mine, but I don't know for sure which front tire size would be best on your bike.

I will say that I really like the Pirelli Sport Demon tires a lot and highly recommend them. I've had my bike for 40 years (60,000+ miles) and the Sport Demons work as well or better than any other tires I've used with the exception of the Michelins with PZ2 racing compound that I used many years ago. Those tires were crazy sticky, but I would go though $600 worth of them per summer (ah, the follies of youth!). Ed

650ed wrote: My bike came with the same size stock rear tire as yours. I run a 120/90 V 18 Sport Demon on the rear, and it is the correct size tire. In the past I ran 130/90 V 18 tires on the rear. They work, but because they are a bit too wide for the rim the cross-section of the tread ends up being a bit distorted and they don't work any better than the 120 size.

My front tire is a different size than yours (3.25-19 instead of 3.50-18). I run a 100/90 V 19 Sport Demon on the front of mine, but I don't know for sure which front tire size would be best on your bike.

I will say that I really like the Pirelli Sport Demon tires a lot and highly recommend them. I've had my bike for 40 years (60,000+ miles) and the Sport Demons work as well or better than any other tires I've used with the exception of the Michelins with PZ2 racing compound that I used many years ago. Those tires were crazy sticky, but I would go though $600 worth of them per summer (ah, the follies of youth!). Ed

Thanks Ed! Appreciate the info!

I agree completely with Ed's recommendations, but I thought I'd add a few comments.

First, I briefly ran a 130 width tire on my Z1R, and it cut a slot in the backside of my chainguard before I noticed. It also was clearly too wide for the rim, with the sidewall very distorted, as Ed mentioned.

I currently have a 120/80 rear bridgestone BT-45 on my bike. It fits fine.

Here is the one bit of interesting information I have to share. The Bridgestone BT-45 is actually available in a 4.00 -18 rear and 3.50-18 front.

Bridgestone BT-45 : www.bridgestone.com/products/motorcycle_...oducts/detail/pr015/
Bridgestone BT-45V :http://www.bridgestone.com/products/motorcycle_tires/products/detail/pr014/

This page gives the width and diameter of the 4.0 and 3.5 tires, so it's easy to compare them to the modern metric size tires.

The 4.0 rear is listed as 119 mm wide and 673 mm diameter. This matches almost exactly to the 120/90-18 BT-45V (121 x 673).

The 3.5 front is listed as 104 x 651, which is between the 100/90-18 BT-45 (100 x 642), the 110/80-18 BT-45V (106 x 630), and the 110/90-18 BT-45V (111 x 655). But none of those seem prefect.

Anyway, the BT-45 is probably not the best tire, but there are so few tires available in 4.0 and 3.5 sizes that I thought it was interesting to compare inch and metric sizes within the same tire line.

dohc wrote: I agree completely with Ed's recommendations, but I thought I'd add a few comments.

First, I briefly ran a 130 width tire on my Z1R, and it cut a slot in the backside of my chainguard before I noticed. It also was clearly too wide for the rim, with the sidewall very distorted, as Ed mentioned.

I currently have a 120/80 rear bridgestone BT-45 on my bike. It fits fine.

Here is the one bit of interesting information I have to share. The Bridgestone BT-45 is actually available in a 4.00 -18 rear and 3.50-18 front.

Bridgestone BT-45 : www.bridgestone.com/products/motorcycle_...oducts/detail/pr015/
Bridgestone BT-45V :http://www.bridgestone.com/products/motorcycle_tires/products/detail/pr014/

This page gives the width and diameter of the 4.0 and 3.5 tires, so it's easy to compare them to the modern metric size tires.

The 4.0 rear is listed as 119 mm wide and 673 mm diameter. This matches almost exactly to the 120/90-18 BT-45V (121 x 673).

The 3.5 front is listed as 104 x 651, which is between the 100/90-18 BT-45 (100 x 642), the 110/80-18 BT-45V (106 x 630), and the 110/90-18 BT-45V (111 x 655). But none of those seem prefect.

Anyway, the BT-45 is probably not the best tire, but there are so few tires available in 4.0 and 3.5 sizes that I thought it was interesting to compare inch and metric sizes within the same tire line.

Awesome post and link.....I was decided on the 120-90-18 for the rear.....but was still trying to decide on the front....I mounted a 110 to see how it looked.....looked way to big....100-90-18 is the way I'm gonna go.

Thanks again!

One other observation on tires -

The sizes marked on tires do not always accurately represent the width of the tires. One should be correct in assuming that all tires of a particular size will be the same width, but unfortunately that is not always the case. Sometimes a tire will be wider or possibly narrower than the size would indicate. The image below shows two Michelin front tires. The tires are from two different time periods and are two different models, but they are both marked on the sidewalls and labels as being 100-90/19 Front tires. Notice the old Michelin A-48 is significantly wider than the much newer Michelin Macadam 50E. Incidentally, the old A-48 tires performed GREAT whereas the newer Macadam 50E tires were about the worse that I ever tired on my KZ650-C1 in 40 years of ownership. Ed