1999 GMC Sierra 1500 Extended Cab Bolt Pattern
Checking fitment for your vehicle? Below you will find the factory bolt pattern (also known as the lug pattern) for the 1999 GMC Sierra 1500 Extended Cab, along with offset and center bore data.
| Bolt Pattern (Lug Pattern) | 6x139.7 (6x5.5") |
|---|---|
| Lug Nut / Bolt Size | 14x1.5 |
| Center Bore (CB) | 78.1 mm |
| Offset (ET) | 20-30 |
| Torque Specs | 100 ft-lbs (135 Nm) |
Imperial Match: 6x139.7 is commonly referred to as 6x5.5" in US Standard.
1999 Sierra 1500 Extended Cab — Year-Specific Fitment Context
The 1999 model year marks the beginning of the GMC Sierra 1500 Extended Cab's 6x139.7 bolt pattern era, which continued through 2013 (15 consecutive years). Wheels from any 1999–2013 GMC Sierra 1500 Extended Cab are cross-compatible with the 1999 model.
GMC Sierra 1500 Extended Cab Bolt Pattern by Year
The table below shows how the Sierra 1500 Extended Cab's wheel specifications have changed over the years. The 1999 model year is highlighted.
| Year | Bolt Pattern | Center Bore | Offset |
|---|---|---|---|
| ▸ 1999 | 6x139.7 | 78.1 | 20-30 |
| 2000 | 6x139.7 | 78.1 | 20-30 |
| 2001 | 6x139.7 | 78.1 | 20-30 |
| 2002 | 6x139.7 | 78.1 | 20-30 |
| 2003 | 6x139.7 | 78.1 | 20-30 |
| 2004 | 6x139.7 | 78.1 | 20-30 |
| 2005 | 6x139.7 | 78.1 | 20-30 |
| 2006 | 6x139.7 | 78.1 | 20-30 |
| 2007 | 6x139.7 | 78.1 | 20-30 |
| 2008 | 6x139.7 | 78.1 | 20-30 |
| 2009 | 6x139.7 | 78.1 | 20-30 |
| 2010 | 6x139.7 | 78.1 | 20-30 |
| 2011 | 6x139.7 | 78.1 | 20-30 |
| 2012 | 6x139.7 | 78.1 | 20-30 |
| 2013 | 6x139.7 | 78.1 | 20-30 |
6x139.7 Pattern Context
This bolt pattern appears on 1067 vehicles in our current database and is considered common.
Examples of other vehicles using 6x139.7:
Expert Buying Guide for 1999 GMC Sierra 1500 Extended Cab
For your 1999 GMC Sierra 1500 Extended Cab, the bolt pattern is 6x139.7mm with a center bore of 78.1mm. When selecting aftermarket wheels, ensure they have a center bore of at least 78.1mm; use hub-centric rings to avoid vibration and ensure proper load distribution. The offset range is 20-30mm; staying within this range prevents rubbing on suspension or body components. Always verify lug nut thread pitch (14x1.5) and seat type—factory wheels use conical (60-degree) seats, while aftermarket may require ball or flat seats. Using incorrect lug nuts can lead to wheel loosening. Re-torque after 50-100 miles of driving.
Historical Fitment Data Reference
In our dataset, GMC Sierra 1500 Extended Cab appears from 1999 to 2013 (15 model years). Across recorded model years, this model generally keeps the same bolt pattern.
- Observed bolt-pattern variants for this model: 1
- Observed center-bore variants for this model: 1
- Observed lug-size variants for this model: 1
- Observed total offset span across years: 50.0 mm
Quick Tips & Safety Warnings
- ✅ Re-torque lug nuts to 140 ft-lbs after 50-100 miles of driving to ensure proper seating.
- ✅ Avoid using wheels from pre-1999 models; they have a different bolt pattern (5x5) and are not compatible.
- ✅ Check for clearance with brake calipers and suspension components when using wheels with offset near 20mm.
- ⚠️ This fitment uses a wide offset range. Check brake clearance and fender clearance before buying wheels.
- ⚠️ Torque lugs in a star pattern to 100 ft-lbs (135 Nm), then re-check torque after 50-100 km (30-60 miles).
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1999 GMC Sierra 1500 Extended Cab — Frequently Asked Questions
What is the bolt pattern for a 1999 GMC Sierra 1500 Extended Cab?
The 1999 GMC Sierra 1500 Extended Cab uses a 6x139.7 bolt pattern (also called lug pattern or PCD). The center bore is 78.1mm and the offset is 20-30mm.
What other years of GMC Sierra 1500 Extended Cab have the same bolt pattern as the 1999?
The GMC Sierra 1500 Extended Cab uses the 6x139.7 pattern from 1999 through 2013. Wheels from any of these model years are dimensionally compatible with the 1999, provided the offset and center bore also match.
How do I measure the bolt pattern on my 1999 GMC?
The 1999 Sierra 1500 Extended Cab uses a 6x139.7 pattern. For 4, 6, or 8-lug wheels, measure center-to-center across opposite holes. For 5-lug, measure from the center of one hole to the back of the opposite hole.
Can I put aftermarket wheels on my 1999 GMC Sierra 1500 Extended Cab?
Absolutely. Just ensure the aftermarket wheels have a 6x139.7 bolt pattern, an offset near 20-30mm, and a center bore of at least 78.1mm (using hub rings if larger).
Will wheels from another GMC fit my 1999 Sierra 1500 Extended Cab?
Only if they share the exact same 6x139.7 bolt pattern, a compatible offset, and a center bore equal to or larger than 78.1mm.
Can I use spacers on my 1999 GMC Sierra 1500 Extended Cab?
Yes, but ensure the wheel spacers match the 6x139.7 bolt pattern and 78.1mm center bore. Also verify that you have enough thread engagement for your 14x1.5 hardware.
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