Team-BHP - Tyre upsizing : Negative effect on the dampers?

Hi, I had a 2004 Honda City GXi which comes with 175/65 R14’s. Three years back, I upgraded to 175/70 R14, for a better ground clearance and more comfort, because for me the ride quality will always be a top priority.

OLD SIDEWALL - 4.5 inches
NEW SIDEWALL - 4.8 inches

This made sure that I wasn’t scrapping her underbelly anymore and I was enjoying superior comfort levels. Around the same time, I realised that the Right Front Shocker had given up. But since it had a remaining shelf life of only 2 years (NCR has banned > 15 year old Petrol cars), I avoided a repair and within a year the Left one gave up too. The car had now done 1,30,000 kms.

Forward to 2019, I upgraded my 2015 Honda Amaze’s 175/65 R14 tyres to the same 175/70 R14. Since I never drive this car, I don’t know how it happened that the Link Rods, the front shockers and Lower Arms, all have weakened up in JUST 40k kms of city usage and the ASC told me to replace them. :Frustrati

So my question is : Was it a sheer coincidence that both the cars needed a replacement after the upsize? Or it’s because of the upsize only? please:
I always believed that an increase in the sidewall reduces the impact force on the shockers, so it shouldn’t have a negative effect on the suspension.

What do you guys think? I am looking forward to upsize my 2007 Honda City CVT tyres from the same 175/65 R14 and I really like what I get from a 175/70 R14. I am NOT in favour of 185/65 R14’s as they will worsen the already underpowered car and steering will feel heavier while parking.

Quote:

Originally Posted by dr.aviansh (Post 4846468)

Forward to 2019, I upgraded my 2015 Honda Amaze’s 175/65 R14 tyres to the same 175/70 R14. Since I never drive this car, I don’t know how it happened that the Link Rods, the front shockers and Lower Arms, all have weakened up in JUST 40k kms of city usage and the ASC told me to replace them. :Frustrati

To my understanding, the increase in the unsprung mass of the suspension setup will increase the impact on the suspension components, and thereby it matters if it were steel rims or alloys. The Alloys may be more forgiving than steel wheels. Did you have alloy wheels on your Amaze?

Lower arms are sturdily built. Are you positive that they need replacement? What if you change only the ball joints and the rod ends?

The factors which impact are

Unsprung weight
Offset
Tire pressure

You may have rims with higher offset leading to higher suspension load. You may be running higher pressure than recommended due to higher perceived flattening of a wider tire.

That said, apart from offset, I rarely see unsprung weight or tire pressure being causes of suspension wear. Offset often can ruin CV joints and other parts

Quote:

Originally Posted by theautoman (Post 4846487)

The upsize you have done is little, my City runs on 205/60R15 on the stock alloys. Factory tire size was 175/65R15.

First of all let’s be clear that even with such a big upsize, the suspensions don’t weaken just like that. Bumpy ride, that’s understandable. The dampers used are trash. They would have well and truly lost their damping over 40000km. But they won’t leak.

Secondly, we need to verify what the ASC is saying. If ends, ball joints or arms are weak, there is corresponding play. Which means your vehicle won’t maintain alignment. Go to any reputed tire shop and ask the staff to check alignment. The first thing they do is verify the soundness of the suspensions. They don’t proceed if any parts are weak and need replacement. Most likely, just the jumping rod bushes are worn, and the ASC is pushing for a full change to make a quick buck off of you.

Quote:

Originally Posted by theautoman (Post 4846487)

did you have alloy wheels in your Amaze?

Quote:

Originally Posted by tsk1979 (Post 4846492)

You may have rims with higher offset leading to higher suspension load.

Hi! Thanks for replying. No, both my cars are on stock steel rims and despite that it happened.

Quote:

Originally Posted by Shreyans_Jain (Post 4846509)

Secondly, we need to verify what the ASC is saying.

See, I took it for a drive and couldn’t agree more to his diagnosis and secondly, my dad is professionally into automobiles and hence quite known to by them, so they wouldn’t be bluffing us anyway.

Yes, your 205/60 R15 upsize has a similar increase in the sidewall like mine.

So, it appears that the upsize wasn’t responsible for both my cars to loosen their springs et al. I’m assuming it to be a coincidence in my case.

Quote:

Originally Posted by Shreyans_Jain (Post 4846509)

we need to verify what the ASC is saying.

Very important. Honda guys love changing suspension components. The would love to change the lower arms every service (10K kms). Only when pointed out that It's been done in the previous service, they change their tone to it's a little weak but you can drive for another 5K kms. And this is done every service.
Unfortunately they have no warranty on OEM replacement parts. So as soon as you drive out after a service, your suspension is due for replacement again.
BTW have been on 185/65/R15 for over 80K kms after the initial 40K kms on stock in my 2008 ZX so no worries. Suspension parts are worn out due to poor quality of the replacement parts compared to what was installed in the factory.