dwsmartins

Hi everyone!

I’m rather obese at 128kg/280lbs (down from 157kg/345lbs) and I ride a 26” MTB style steel commuter. It has a pretty robust frame and fork, definitely not a feather, but surely strong. For 9 years or so, I‘ve been building it to withstand my heavy weight and I’d like some opinions about what I’ve done so far and what should I do next.

The current frame is from BTwin. The previous one was a similar from Caloi, a local brand from the Dorel group, which has endured 8 years of reliable service, retired due to a mounting error (my bad...) resulting in permanent damage. The actual is surely better built, with lifetime warranty. I know it’s intended use and will certainly not make a downhill with it.

I’ve choose a 26” frame based on my belief that a smaller wheel is stronger than a bigger one, assuming all else (materials, build techniques, etc.) is the same. The smallest frame for my size, foldable ones excluded, is 26”, and I think this was a sound decision, as I hadn’t any wheel related problems on the last 9 years of cycling.

For the wheel buildup, both are 36 holes with locally sourced mystery spokes and nipples from Isapa, a local distributor of bike parts. I call then “mystery” because they don’t have any markings, but they’re stainless steel non-butted spokes (non magnetic, so they’re not galvanized steel) and the nipples are probably silver coated brass, as they’re definitely not aluminum. These are used on cargo bikes around here, so I think they’re just dumb strong.

The wheels where hand built by a reputable and experienced wheel builder, who also became a friend of mine, so I guess I can trust him. The hubs are Shimano HB-RM40 front and FH-RM30-8 rear, laced to a pair of double walled downhill rims with stainless steel eyelets (VMaxx from VZan, another local brand). Those rims are quite heavy, weighting 800g/1.75lbs each, but are also famous for being bombproof. Amateur downhillers use it a lot around here.

The handlebar and stem are aluminum 31.8mm/1 1/4”, both from BTwin. I’ve replaced the 25.4mm/1” ones which came on the bike for greater resistance (more diameter, more strength, I guess). The stem is aheadset type with 35° rise (the frame is not suspension corrected, so is quite low on the front) and the handlebar has 5° upsweep, 9° backsweep and 15mm rise. They’re torqued to specs, with blue Locktite added for precaution.

The front fork is something of concern, as it’s a threaded oversized one. Actually I use a matching aheadset adapter to make it possible to install the stem, very similar to the one below:

But I know the best bet would be a true aheadset config. I’m thinking about ordering a bespoke chromoly fork from a local frame builder, as I can’t find one on the local market and the import taxes make it more expensive than building it with a reputable professional. This is on my to-do list.

The v-brakes are good quality, but I don’t remember the brand and the markings have vanished. Their plastic coil covers have became brittle due to aging (9 years), but they’re fully functional. I’m planning to replace then with Shimano BR-M422 or BR-M4000, commonly found around here. Do you recommend any other?

The drivetrain is 24spd, commandeered by a pair of Shimano ST-EF500 EZ Fire brifters mated to FD-M371 and RD-M370 derailleurs. Bottom bracket is UN-BB26 square taper, the second one I’ve installed (the previous have more than 10000km/6000mi on it, so I guess it’s reliable). I also know the derailleur are 27spd and I’ve got some chain rubbing on the front, but don’t know if that’s the cause of it, more on that later.

4 months ago I’ve installed a SunRace FCM918 48-36-26T chainset, SunRace CSM980 11-40T 8spd cassete and SunRace CNM84 8spd chain. These parts are the reason I’ve decided to post here, as I’ve managed to bend the fifth cog of the cassete over the sixth (never heard of or see anything like that!) and found the chainring had a slightly misaligned hole for the square taper bottom bracket, a sure cause for chain rub.

Right now I’m planning what to do next. I’d really like to keep the wide range, and already found a Shimano FC-T4060 chainset with SM-BB52 bottom bracket. The remaining decision is about the cassete: will an 8spd chain and cassete work without the annoying chain rub or I’ll must migrate to 27spd?

Also there’s another question: how zinc/chrome plated cassetes compare to phosphate (black) ones durability wise? My previous (and now current, as it’s back on duty) cassete was a Shimano CS-HG50-8 with 11-34T and that’s my reference point, as it lasted more than 6000km/4000mi (any new chain skips on it, so my previous KMC chain is also back).

Sorry for the long text and thanks for those reaching this far. Please, hit me with your answers and opinions, wether it’s good or bad. Constructive criticism means good teachings, so bring it on!

Bill Kapaun

I've had the DS cone want to pit on the FH-RM30 hub. (would expect the same on the RM40, since it has a common cone with the RM30)
Grease the bearings well before putting in use.
I unfortunately used that hub to build 3 wheels.
ALL were too tight and had minimal grease.
I'm hoping synthetic lube will help reduce the problem,

HillRider

I think your chain rub problem is due to the misaligned crank, not inherent in a 3x8 drivetrain. Replacing the crank is likely to fix it and, if you can find a replacement cassette with the gearing you want, there is no reason to go to "27-speed", i.e. a 9-speed cassette.

A proper threadless fork and headset will be fine but your current threaded fork/headset with an threadless stem adapter seems to be working so far.

bpcyclist

I think you should stop using the word "obese" to refer to yourself. I personally believe it is an unkind, mean, even, pejorative term that fails to acknowledge the absolutely incredible job you've done getting your weight down from where it was. Awesome job!!

Bill Kapaun

IF you need low gears, else why a 40T cog?) install a 22-32-44 crankset.

WHEN your R. shifter dies is the time to upgrade to 9 speed for a much better cost/benefit ratio.
I admit I upgraded my hybrid to 9, but I need gearing that just isn't as easily available in 8 speed.

dwsmartins

Thanks for the advise. The FH-RM30/HB-RM40 are sold as a pair by the Shimano local distributor here in Brazil. In fact, they’re the only option I’ve found on the Shimano catalog here for 36 holes (they’re pushing the market to 32 or less).

I’ve found a pair of 36 holes FH-RM70/HB-RM70 on the local version of eBay, through. They’re not from the local distributor: these were directly imported, according to the seller. Assuming they’re legit, are they worth the upgrade?

By the way, my wife’s bike is much more basic, so if I just pass these hubs for her that’ll be really an upgrade, so I won’t spend (completely) in vain.

dwsmartins

I really hope the change of crankset solves the chain rub! That noise is annoying! Maybe I can buy in steps: first the chainset/bottom bracket, do a quick test with the 8spd cassete and, if all goes well, I buy a new 8spd cassete and 8spd chain. What I can’t do is use the new chainset with the old chain/cassete, as I guess it’ll ruin it.

As for the fork, I’m quite OK at it, but it seems to develop some play quite fast, about once every two weeks. An aheadset fork/bearings should solve this, with the added benefit of better durability, am I wrong?

dwsmartins

Thanks for the support, man! But “obese” is a medical term, not an insult, despite a lot of people use it this way. I’m positive, through: before any weight loss, I was classified as “morbidly obese”. I surely got some progress!

dwsmartins

I need low AND high gears, trust me. I’m somewhat a masher and it’s really comfortable for me to slowly pedal at 60-70RPM at the longest gear on flat sections at about 35km/h/22mph. On the other hand, my town has some considerable climbs, so a wide ratio is really useful.

The bent SunRace cassete was to solve this: a 26/40 lowest gear to climb walls and a 48/11 to cruise on flats and keep pushing on the descents. I’m truly sorry that cassete wasn’t as robust as Shimano’s.

As for the shifter, I can install it on my wife’s bike, but it’ll really make more sense financially if I wait for it to grind to a halt. I’ll make it logical and reasonable: I’ll do a quick test just as I’ve described on a previous reply. If the chain rub vanishes, I’ll buy just the 8spd cassete and chain to replace the worn ones; else, I’ll bite the bullet and buy 9spd shifters, cassete and chain.

Bill Kapaun

Since the wheels are already built, I'd take an aggressive, pre-emptive approach to servicing the hub.
Stock up on Bearing Balls & a tub of good grease.
This cone also fits the RM30 on both sides.
https://www.sjscycles.co.uk/hub-spar...03000/?geoc=US
You might want a couple spares in case you do run into pitting.

I would no longer build a wheel using less than Deore quality hubs.

shelbyfv

I disagree. Obese is a legitimate medical term that apparently accurately describes OP. FWIW, we have an entire forum section devoted to Clydes. While Clydes are not necessarily obese, many are. Facts are facts.

Bill Kapaun

+1
The OP has earned the right to use whatever terminology they desire.
IF it offends people that are even more obese, maybe that's the slap on the head they need.
Being an apologist doesn't do them a bit of good.
BTW, I used to weigh 115 lbs. more than I do now. 298 >183.

bpcyclist

You are quite obviously certainly entitled to your take, though I don't share it. That said, I hve been tall and quite thin my entire life--just to be clear. At one point in my life, I performed gastric bypass surgery for a living, so I do have a bit of experience in this milieu.

That said, this topic has actually been fairly carefully studied by endocrine researchers. The term "obese" repeatedly scores at or near the bottom in desirability on the part of people dealing with serious weight issues as a descriptor for their problems. Most don't like it. The most favorable term most often described as being one those in this situation would like to have used is "weight problem" or having a "BMI" issue. This is what the research shows.

The people I used to operate on, the overwhelming majority of them, had been on every kind of diet imaginable. Many had been exercising regularly. But for a variety of reasons, taking the weight off is just extremely difficult for some subsets of patients. It's not about being an apologist. It's about providing support and expressing empathy to people with a life-threatening medical issue. That's something I think anyone with a soul can get behind.

Bill Kapaun

Maybe if there weren't so many apologists & enablers, the problem wouldn't be so wide spread.

2old

Seems to me that we should focus on the bike build instead of the definition of obese. I ride MTB exclusively so not s good judge of road-type components, but think the OP is on the right track. I've had good luck with 8-speed Shimano Altus components on eMTB and 9-speed DeoreXT on MTB where lower gearing is desirable. Only suggestion for lower gearing is a 20 or 22 tooth chainring if it's feasible.

dwsmartins

Please, fellows! Let’s get the obese or whatever discussion to healthcare forum.

I personally don’t care about it as I don’t take as an offense, but I know there are people who do. I share bpcyclist’s vision, through: empathy must be in order for those who suffer, whatever reason it may be.

cb400bill

Thread closed for Moderator discussion.

cb400bill

Thread reopened. Stay on topic.

bpcyclist, do not post in this thread again.

wrk101

On chain rub, read up on cross chaining. On MTB/ATB, I prefer friction shifting for the front derailleur as you can quickly trim the derailleur to wherever you need it. I also prefer trigger or thumb shifters over the rapid fire shifters. If you are cross chaining with an indexed front shifter, chain rub is not unusual.

Cheapest way to reduce weight on a rigid frame MTB is getting lighter weight tires, and to a lesser extent, tubes.

On wheels, I would prefer your current, hand built wheels over a machined built replacement. When it comes time to replace, I would talk to that local builder about getting a new set built.


Congratulations on the weight loss!

tomtomtom123

You will almost always get chain rub on the FD with index shifters when using triple chainrings, when you cross-chain from big-big to small-small big-small or small-big, due to the increased chain angle when trying to run the chain all the way across the inside to outside of the drivetrain. In such a case, if you don't want chain rub, then you should only use the inner cogs with the inner chainring, and the outer cogs with the outer chainring. The range of the middle chainring without chain rub depends on how the drivetrain is setup. You can put your bike on a workstand, or just prop up the rear, and shift through the entire gear range to determine at what gear combination you can use without chain rub, and then memorize it. You could also readjust your FD swing/pivot, FD limit screws and cable tension so that there is less chain rub, while still being able to shift reliably.

A double chainring with a SRAM YAW road FD does not have chain rub, and does not need trim. This is because the front of the FD cage is much wider than a Shimano FD cage, and the YAW design pivots the cage so that the front and rear move at different rates when shifting. I can't remember if the front or the rear is the end that moves further, I think it was the front. However, if you have a MTB bike and you want to convert to double chainrings and use the YAW FD, you have to find out if the FD clamp ring will match the usually thicker diameter seat tube of a MTB bike, or the braze on position or the swing range of the FD will be able to reach further outwards for the more outward chainline of a MTB crank, compared to a road chainline.

Bill Kapaun

Referring back to racing down hill-
I think I can safely say that most of us "tuck in" and try to be "more aero" going down hill and save our energy for the up hill part.
The faster you go, the effect of air drag increases VERY disproportionately. You WASTE more energy.

Constant "mashing" will make your knees old before their time.

Experiment with seat height. When I'm "riding regularly", I can tell the difference from a 1/8" adjustment.

Being formerly rather rotund on the posterior, I used a rather wide saddle.
Having been gifted an 87' Rockhopper after my '86 was stolen, I tried the narrower saddle it was equipped with. It was a "deal with it", because you've already spent too much money doing the more important things, like a 165mm crank length. KNEES!!!!! Just doing some slow test riding, doing the fine tuning of the DER adjustments, my knees were hurting after 6 blocks w/175mm cranks. 170's and I have knee pain more often than not.
Anyway, the narrower seat was so much more efficient. I could raise it higher and get "more time" in the "power stroke" part of the push.
I was able to near the same max speeds as before while being in much worse physical condition. (look up BCG treatments/fatigue)
As you lose weight, you might explore that option. IF you have the ability to try a SLIGHTLY narrower saddle then you currently use, explore-

dwsmartins

I don’t cross chain. In fact, I’m quite methodical about bad practices: I’ve created a spreadsheet with all gear ratio combinations, compared for overlap, and choose those I considered adequate. In my case was 1-5 with the granny, 4-7 with the middle and 6-8 with the larger. The bent driveside crank is surely the main cause for chain rub, I wasn’t sure if it was the only one.

My tires aren’t lightweight, but my inner tubes are. The pavement on the streets around here is very bad, so I never considered light tires fearing low durability. But thanks for the suggestion!

My next set of wheels will be surely built by this friend of mine, but I surely hope they endure a lot!