New Tires...Brand and Size

[MT45]

Thought I’d share my findings for installing the ContiPro Contact 175/55/r15 car tires on my 2019 Spyder RT Limited
I’ll start with the answer. They don’t fit.

Based on many threads here I had my fingers crossed that maybe they would be a simple bolt on. No luck … BUT the solution for me was not that difficult

The fix:
Part A
Replace all 4 hex head screws (#8 x 9/16”) that connect the black part of the plastic fender to the colored (painted) Tupperware part. This will lower the overall profile of these screws
Part B
Install some 1/4” nylon shims and longer screws (#8 x 3/4”) You’ll use these to effectively push the fender assembly back off its steel mounts by 1/4” toward to center of the bike and effectively away from the tire

Parts list:
1/4” thick, 3/8” OD nylon shims (8 pieces)
#8 x 9/16” long Trusshead screws (8 pieces)
#8 x 3/4” long Trusshead screws (8 pieces)

The fix in part A calls for 4 pieces of 9/16” screws (each side) are mostly appreciated in the top and bottom portions of the fender where the tire comes closest. These screws hold the black ABS plastic to the colored bits of Tupperware that make up the fender top. Replacing these 4 screws lowers the profile of that area by a few millimeters and that’s a good thing because these screws are the main area the tire wants to rub AND is also the most dangerous. The lower screw on the inside of the fender (toward back of bike and closest to ground). The tire can exert tremendous pressure on this screw/mounting area based on the tire rotation hitting that screw in a “push into” manner (vs the top inside screw where a tire rub would be pushing away). Hard contact with that lower screw could literally (and probably instantly) rip the entire fender off the steel mounts. That lower screw is the main concern and with the fix I did here it completely eliminated it as a potential problem.

In part B, you are creating an additional 1/4” of space between the fender and the tire (and, of course the 4 screws you just installed) by installing nylon spacers BEHIND the metal fender bracket and the black ABS portion of the fender plastic.
Note that I did try to run the tires with only replacing the 4 fender hex head screws (no shims) but got extensive rubbing simply driving straight and was marking the tires during aggressive cornering. Shims are the way to go.

LATE EDIT - NOTICE VERY SLIGHT RUBBING INSIDE OF TIRE
Just noticed the wire wraps that capture the wiring running up the vertical frame rail that the fender is mounted on are just slightly rubbing one side (inside of the tire)
See the images and note how I fixed by adding 2 pieces of 3/16" thick washers to the inside of where that frame rail mounts
Pulls the entire assembly toward the inside (center) of the bike and away from the tire - now clears by more than an 1/8"
IMG_5342.jpg
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IMG_5344.jpg

[BLUEKNIGHT911]

I'm surprised you had a fitment issue .... others here have been using this size on other Spyders ( but we've learned not all tires are excactly the same size for the size printed on the tire ) .... it could be the 2019 are made slightly different than past years .... but have done what I did years ago to fix the issue ..... thanks for sharing ..... and Nice pics .... Mike

[MT45]

I'm surprised you had a fitment issue .... others here have been using this size on other Spyders ( but we've learned not all tires are excactly the same size for the size printed on the tire ) .... it could be the 2019 are made slightly different than past years .... but have done what I did years ago to fix the issue ..... thanks for sharing ..... and Nice pics .... Mike

I was surprised too Mike but I'm not sure I ever saw anyone with a '19 try these tires. Quite a few earlier years than 2019 worked without modification according to the forums here.

Also, full credit to you for the spacer idea! I knew I had read that somewhere!

[BLUEKNIGHT911]

I was surprised too Mike but I'm not sure I ever saw anyone with a '19 try these tires. Quite a few earlier years than 2019 worked without modification according to the forums here.

Also, full credit to you for the spacer idea! I knew I had read that somewhere!

Thanks for the compliment ..... Although I said the year Spyder ( 2019 ) might be the issue, The BRAND of tire may really be the issue .... From reports on the forum many.many folks have been using Vredestein Q-5 and Quatrac models in 175/55-15 on all years of RT's ..... I discovered that the General Altmax RT 43 is larger than normal in 175/65-15 size .... I had to shim that one to get it to fit my 14 RT ( with basic fenders ) Both Peter and I have stressed the fact that tire charts are " mathematical " sizes, actual tire sizes can be quite different ..... glad it worked out for you ...Mike

[mecsw500]

One has to be careful when dealing with the roiling circumference of a tire versus its static unloaded stationary circumference. The real, or rolling circumference, is effected by the tire construction, the tire pressure and the speed of rotation at which it is calculated (I think DIN spec says that is 60 kmh) and probably half a dozen other criteria.

So, when comparing a car tire with the OEM tires, there will probably be a circumference difference down to the stiffness of the sidewall construction and the air pressure utilized, as well as of course the fact that manufacturers dimensions may not actually be what exactly is stamped on the tire.

Ignoring the speed issue, about the only way to really measure the real rolling circumference is to mark the tread with a dab of paint and then roll it across the garage floor and measure the distance between the marks it leaves.

Apparently a good approximation is to measure the radius from the center of the hub to the highest point of the tire, then measure the radius from the center of the hub to the ground, at the pressure you normally use. Then you can calculate the rolling circumference (at 0 speed) by taking the average of the two radii values and calculating the circumference for the tire with the equation C=2(pi)r, where C is the rolling circumference and r is the average radius you measured.

From what I can tell, the nearest real rolling circumference to the Kendra in available car sizes, is 165/55R15, then 175/55R15 followed by 165/60R15. Of course the 175 may or may not fit the fender. On the rear the 225/50R15 and then 205/55R15 seem to be really close to the OEM Kendra as well.

The Kendras that came stock on my 2021 RT Limited to be fair I don't think aren't that bad, in the dry or the wet. They seem to stick OK and they feel alright to my mind and the front / back feel seems well matched. Mileage we will have to wait and see. Your mileage may vary, quite literally, of course.

Merry Christmas everyone.