Forum Discussion
BurbMan
Jan 13, 2015Explorer II
Ummm...OK...I see that math was not your strongest subject. Let me see if I can clarify.
You are correct, the 245, 265, 285, etc, refer to the width of the tire in millimeters. The second number, the "75", is the aspect ratio, which is the ratio of height to width. So, if you increase the width and keep the aspect ratio the same, the diameter of the tire will increase too. Sorry if I wasn't clear on that.
The calculator that I linked to is 100% accurate. You are correct that it is linear, because geometry is linear. If you increase the diameter of a tire by 2" it will have the exact same effect on the gear ratio on any vehicle, whether it is a large truck or a mini cooper. It would be a smaller % change on the large truck, but the numerical change is the same.
I don't need to justify myself, it's just math is all. Sorry if you don't get it.
The FACT is, you reduced your towing power with those taller tires on your truck...but if you are satisfied with how it drives, that's all that matters...it's your truck not mine.
I only posted this info so that the OP could take this into account when lifting the truck he uses to tow a 35' trailer.
majorgator wrote:
You referred to the tire WIDTH and referenced that as the tire HEIGHT. The second number in this method of tire sizing gives reference to the height. I never said anything about gear changes.
You are correct, the 245, 265, 285, etc, refer to the width of the tire in millimeters. The second number, the "75", is the aspect ratio, which is the ratio of height to width. So, if you increase the width and keep the aspect ratio the same, the diameter of the tire will increase too. Sorry if I wasn't clear on that.
majorgator wrote:
The calculator you linked to is not accurate. It depends on linear data input and provides linear data outputs. As stock tire size increases, the calculator becomes less accurate, because overall diameter increases become less of a factor. If you increase the diameter of a compact car tire by 2", then you've made a huge change. But when you increase a large heavy duty tire diameter by 2", you've created an almost negligible impact. A straight-line calculator cannot deal with this.
The calculator that I linked to is 100% accurate. You are correct that it is linear, because geometry is linear. If you increase the diameter of a tire by 2" it will have the exact same effect on the gear ratio on any vehicle, whether it is a large truck or a mini cooper. It would be a smaller % change on the large truck, but the numerical change is the same.
majorgator wrote:
Don't be so quick to justify yourself that you fail to read.
I don't need to justify myself, it's just math is all. Sorry if you don't get it.
The FACT is, you reduced your towing power with those taller tires on your truck...but if you are satisfied with how it drives, that's all that matters...it's your truck not mine.
I only posted this info so that the OP could take this into account when lifting the truck he uses to tow a 35' trailer.
About Travel Trailer Group
44,030 PostsLatest Activity: Jan 21, 2025